Quite simply stackoverflow.com is a question and answer site for programmers.

From the about page:

Stack Overflow is a programming Q & A site that’s free. Free to ask questions, free to answer questions, free to read, free to index, built with plain old HTML, no fake rot13 text on the home page, no scammy google-cloaking tactics, no salespeople, no JavaScript windows dropping down in front of the answer asking for $12.95 to go away. You can register if you want to collect karma and win valuable flair that will appear next to your name, but otherwise, it’s just free. And fast. Very, very fast.

We don’t run Stack Overflow. You do. Stack Overflow is collaboratively built and maintained by your fellow programmers. Once the system learns to trust you, you’ll be able to edit anything, much like Wikipedia. With your help, we can build good answers to every imaginable programming question together. No matter what programming language you use, or what operating system you call home — better programming is our goal.

Stack Overflow is as frictionless and painless to use as we could make it. We believe finding the right answer to your programming questions should be as easy as falling into the pit of success. And maybe even a little fun along the way.