Hello! Welcome to the Unity subwiki. This space is for programmers and designers to share their experience and tips in the Unity Engine.
First things first: if you want to use Unity, you should probably go to their website. In general, we suggest the free personal version. Both of these links will detect if your OS is Windows or Mac.
If for some reason you're looking for older versions of Unity, look here.
Finally, if you're looking to get Unity running on a Linux machine, you're likely to have a hell of a time. The latest Linux is always a number of releases behind the latest Windows and Mac versions too. That said, here are some handy links: