If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one.
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.
It's a programming language and environment which is widely used in the statistical community, in part because it has a LOT of statistics-related libraries available for it.
Historically, it's an open-source re-implementation of the programming language S developed at Bell Labs in mid-70s.