This is a guide I wrote 4 years ago for the LobCorp subreddit and Project Moon fan discord.
After having issues with my reddit account, I'm reposting the guide here for future players who are looking for quick details on how resetting works.

• Can be chosen in the Pause menu at anytime during gameplay.
  
• Returns you to the Deployment Phase of the current day.
  
• This does NOT allow you to change which abnormality you picked for the day.
  
• Any E.G.O., Employee Levels, PE-Boxes, and Abnormality Observations unlocked during the day before the Retry are lost.
  
• Any employees and E.G.O. that were lost during the day are returned.

This method of restarting is a way to restart the current day you are on in the event that you made a critical mistake, such as losing all of your most valueable employees and/or equiped E.G.O gear. However, this also means that any progress you've made into the day will be lost as well.

• This type of reset returns you to beginning of your 5 day week (Day 1, Day 6, Day 11, and so on...)
  
• Each of the Days that begins your week you'll be notified that the Memory Repository has been imprinted.
  
• Compared to Retrying the Day, Rewinding the Memory Repository allows you to keep all E.G.O gear you've obtained throughout the week, any Abnormality observations unlocked, and any Department Missions you completed will remain finished.
  
• All Employee levels are reset to what they were at the beginning of the week.

This method of restarting is a great way for obtaining E.G.O. and observational information from Abnormalities that are too difficult to keep contained throughout your entire playthrough. It is also a good way to finish Department Missions that result in a high number of deaths.

• You can choose to completely restart from the 1st day if things get too uncontrollable for you and Rewinding won't fix it.
  
• This is done by choose "First Day" in the menu at the start of the game.
  
• All E.G.O. and unlocked observations will be retained, like in a Rewind.
  
• All employees and levels will be lost.
  
• Any Abnormalities currently being contained will be lost (But your Observational Levels and PE Boxes will not be lost.)
  
• Any Department Missions finished will remained finished.

This is a way to restart the game should you find yourself having hit a brick wall in terms of progression, such as your currently contained Abnormalities being too difficult to manage, and Rewinding can't fix it.

Ultimately the various methods of retrying and restarting are vital to the Lobotomy Corporation experience, and attempting to finish the game without utilizing them is near impossible. Do not worry if you feel like you're retrying or rewinding a lot, as I guarantee most LobCorp Veterans have utilized restarts, rewinds, and retrys more than they care to admit.