More details on the history of Linux can be found the book Inside Linux by Randolph Bentson <firstname.lastname@example.org> (see the section called Books in Chapter 11 for more information about this book).
Linux is a freely available operating system for PCs: to be more precise, it is one of many flavors of Unix. Linux is being developed on the Internet by several thousand people, first and foremost by Linus Torvalds <email@example.com>, who created Linux for the 80386 in 1991. Linux is being tested and used by many more (the total is thought to be in the hundreds of thousands, perhaps millions).
At the time, Linus believed that Linux was inherently Intel-specific. A few Amiga and Atari hackers were determined to prove him wrong.