X4 Foundations is a game unlike anything you're likely to have played before outside the X series.

A proper description, after thousands of hours of gameplay is tough to put into a quick overview.
How would you describe the universe and your place in it.
X4 is more than just a beautiful space flight sim.

Perhaps starting at the beginning.

In the beginning, Egosoft created the universe. Beautiful, breathtaking and expansive with multiple races and factions each with their own political, economic and military goals. A living breathing economy based on supply and demand governs the creation of new ships and stations for each of the factions. The ships range in size from "Compact car" sized small fighters and scouts to several kilometer long battleships.

Starting a new game, the player (Different game starts available) enters the universe with a "Compact car" sized ship and is introduced to a story arc. (Of which there are several)
The story arcs are all optional and will wait for you to find and do them.
Many require a great deal of resources to complete.
Completion of the arcs can have profound effects for the factions involved.
War and peace, creation or destruction.

What you choose to do in the meantime, is completely up to you.
With your player faction, a sample size n=1 (Just You), you might start mining crystals in asteroid fields, trading, mining resources, hunting pirates and aggressive ships, doing missions for the various stations and factions, piracy, or just exploring the universe.

Personal success permitting, you may buy (or acquire) more ships, Hire crew and put them to work for you mining and trading for other factions. Perhaps building your own stations and having the ships work directly for your station managers is more your style. Setting up your own supply chain and shipyards has it's advantages. Taking control of sectors for your faction and setting up a local police force also has benefits.

X4 is not like most games in the traditional sense.
Traditional meaning: You buy it, Play through a scripted story on rails, Yay, you're an incredible hero. Game over. (This is NOT X4)
The story arcs in X4 have some internal significance but the universe ticks on regardless.
The "storyline" analogy is more a focus on the player and the faction built by the player.
You play the game your way. Sandbox Universe Game.
Becoming personally rich and having a powerful faction is somewhat anti-climactic.
Doing what you enjoy and enjoying what you do is much more rewarding as far as I'm concerned.
This persists past the point where you have nothing more to spend money on.

Egosoft's business model appears to be increasing the universe with expansions which also helps to fund ongoing development in X4. UI improvements, additional functionality, a recent Engine rework, bug fixes etc.
The game has changed a lot from release. Numerous features have been added. Some, not documented sufficiently in game.

I would recommend, if you decide to purchase X4, to also join the Egosoft forums. People are friendly and questions asked are answered often. Recommendations for improvement are taken under advisement by Egosoft. They are well invested in making the best game possible. Bug reports are looked into.

There is also a public beta branch if you wish to be involved in testing and feedback of new features and changes. Bleeding edge does involve blood at times (Beta bugs). Outsourced testing like this works well as players and developers all want the best game possible. Developers get direct feedback on changes and can put more resources towards coding than internal testing. Keeping the finger on the pulse of players and always having a multitude of fresh perspectives is an added bonus.

The forums are definitely an integral part of an interesting ecosystem. One that works well.

X4 is a great game with ongoing development.
Not everything about X4 is positive though.

Sometimes new features and new updates add bugs to the stable branch of the game if missed in beta.
New features often don't come with documentation.
The game doesn't cater to the new players or seasoned veterans leaving a reasonable learning curve in the beginning for newcomers and requiring early game contingency plans for veterans to ensure challenges later.

From a Player perspective, I've had a pretty good return on investment (Hours of entertainment vs money spent.)
If space sim games are your type of game and that metric is of any meaning to you, watch some gameplay videos to see if it's your type of game too. Many of the Egosoft videos on Steam are like movie trailers. Yes, its a beautiful game... Watch a few minutes of actual gameplay for context as well. The schizophrenic series of awesome clips typical of trailers doesn't tell you much of gameplay.

X4 Foundations is a game unlike anything you're likely to have played before outside the X series. A proper description, after thousands of hours of gameplay is tough to put into a quick overview. How would you describe the universe and your place in it. X4 is more than just a beautiful space flight sim. Perhaps starting at the beginning. In the beginning, Egosoft created the universe. Beautiful, breathtaking and expansive with multiple races and factions each with their own political, economic and military goals. A living breathing economy based on supply and demand governs the creation of new ships and stations for each of the factions. The ships range in size from "Compact car" sized small fighters and scouts to several kilometer long battleships. Starting a new game, the player (Different game starts available) enters the universe with a "Compact car" sized ship and is introduced to a story arc. (Of which there are several) The story arcs are all optional and will wait for you to find and do them. Many require a great deal of resources to complete. Completion of the arcs can have profound effects for the factions involved. War and peace, creation or destruction. What you choose to do in the meantime, is completely up to you. With your player faction, a sample size n=1 (Just You), you might start mining crystals in asteroid fields, trading, mining resources, hunting pirates and aggressive ships, doing missions for the various stations and factions, piracy, or just exploring the universe. Personal success permitting, you may buy (or acquire) more ships, Hire crew and put them to work for you mining and trading for other factions. Perhaps building your own stations and having the ships work directly for your station managers is more your style. Setting up your own supply chain and shipyards has it's advantages. Taking control of sectors for your faction and setting up a local police force also has benefits. X4 is not like most games in the traditional sense. Traditional meaning: You buy it, Play through a scripted story on rails, Yay, you're an incredible hero. Game over. (This is NOT X4) The story arcs in X4 have some internal significance but the universe ticks on regardless. The "storyline" analogy is more a focus on the player and the faction built by the player. You play the game your way. Sandbox Universe Game. Becoming personally rich and having a powerful faction is somewhat anti-climactic. Doing what you enjoy and enjoying what you do is much more rewarding as far as I'm concerned. This persists past the point where you have nothing more to spend money on. Egosoft's business model appears to be increasing the universe with expansions which also helps to fund ongoing development in X4. UI improvements, additional functionality, a recent Engine rework, bug fixes etc. The game has changed a lot from release. Numerous features have been added. Some, not documented sufficiently in game. I would recommend, if you decide to purchase X4, to also join the Egosoft forums. People are friendly and questions asked are answered often. Recommendations for improvement are taken under advisement by Egosoft. They are well invested in making the best game possible. Bug reports are looked into. There is also a public beta branch if you wish to be involved in testing and feedback of new features and changes. Bleeding edge does involve blood at times (Beta bugs). Outsourced testing like this works well as players and developers all want the best game possible. Developers get direct feedback on changes and can put more resources towards coding than internal testing. Keeping the finger on the pulse of players and always having a multitude of fresh perspectives is an added bonus. The forums are definitely an integral part of an interesting ecosystem. One that works well. X4 is a great game with ongoing development. Not everything about X4 is positive though. Sometimes new features and new updates add bugs to the stable branch of the game if missed in beta. New features often don't come with documentation. The game doesn't cater to the new players or seasoned veterans leaving a reasonable learning curve in the beginning for newcomers and requiring early game contingency plans for veterans to ensure challenges later. From a Player perspective, I've had a pretty good return on investment (Hours of entertainment vs money spent.) If space sim games are your type of game and that metric is of any meaning to you, watch some gameplay videos to see if it's your type of game too. Many of the Egosoft videos on Steam are like movie trailers. Yes, its a beautiful game... Watch a few minutes of actual gameplay for context as well. The schizophrenic series of awesome clips typical of trailers doesn't tell you much of gameplay.