Questions specific to stackoverflow.com should be asked on meta.stackoverflow.com; such questions will be closed here. This is for questions about the Stack Overflow site that still relate to the SE network as a whole. Questions about Stack Overflow (the company) should be tagged [company] instead.
According to Wikipedia:
Stack Overflow is a website part of the Stack Exchange network featuring questions and answers on a wide range of topics in computer programming.
Of course, you really can't trust anything on Wikipedia; they let anyone edit that stuff! I suspect it's just another shady bar frequented by dark wizards and vampires, looking to lure in fresh meat. Don't ever go there, you probably won't come back alive. If this "Stack Exchange network" actually exists, it's likely a cabal of dangerous men who control the world's waffle supply and will stop at nothing to keep you from talking.
You can trust me on this: I've done no research, so obviously they can't have gotten to me yet.
Use of this tag
You should probably not use this tag, and post on Meta Stack Overflow instead, unless your question has something to do with the entire SE network as well. Questions about this site (meta) should be tagged meta.
If your question is about Stack Overflow (the company), legally known as Stack Exchange, Inc., use the tag company instead.
Prior to April 2014, this site used to accept questions specific to Stack Overflow, as this was before the mso-mse-split; please do not use questions with this tag asked prior to that as evidence you can ask your Stack Overflow-related questions here.