You can do it the way you like.
You can download just 1, 2 or 3 at once.

But they will always download 1 game at a time. :)
Same with updates too.

Originally posted by curtis_9557:

If i purchase 3 steam games how do i receive them? by download? and if so, are they all downloaded at the same time? thanks

You need to download and install the Steam Client software.

Log into the Steam client. In the Library section of the client you should see the games you've purchased. You can download them and manage them from the library.

You can download them whenever you want, it's not a one time only or time limited option. Games are downloaded and updated one at a time.