We have a sticky that explains what the badges under members' names are, but a Guru in particular is basically anybody who has demonstrated that they are actively trying to be a part of the phpfreaks community and in general know wtf they are talking about. You don't have to be some super ninja expert at everything, nor do you have to be posting 100 posts a day to achieve this rank.
Traditionally the process for "gaining rank" around here involves you joining our community and making an effort to help others out with their questions. And after a while of this, one or more members of the staff (guru, mod or admin) may take notice of your efforts and then nominate you to join the ranks (this happens internally). In addition, we try to look at things like rep and posts marked solved to find you.
But maybe you feel like you've been making an effort for naught. Most of us don't regular all the forums; we just hang around the ones we are the strongest at or most interested in. So maybe the one thing you're really good at is the one forum nobody else really hangs out in. Or maybe the stars just don't seem to align right or something.
So, in order to ensure that nobody feels like they are going unnoticed, I want to extend the nomination process to the entire community. If you feel like you've been hanging around and helping out for a while and have what it takes to wear a Guru badge, or if you know someone around here who does, please post your nominations here, as a way to ensure yourself or someone else is on our radar.