If you use Linux at all (and in many cases these days, even if you don't), you have heard of the open source Linux compiler called GNU Compiler Collection, or GCC for short. It's the most common compiler used, shipping with almost all distributions of Linux, and it's actually older than Linux itself.
A compiler transforms one computer language into another, generally making the code executable and machine-readable. Way back in 1984, programmer Richard Stallman wrote a C compiler called GNU C Compiler. GNU stands for "GNU's Not Unix," a common naming convention for hackers at the time.
Linus Torvalds announced that he was using GCC 1.40 in his new Linux operating system. The rest of that story is history.