What's with # and @ in facebook/twitter?

[sauconyride]

I notice people using this a lot lately on facebook. I understand that when you hit the @ button, it gives you a list of friends you have the option of tagging in a given post, but the # button is confusing me.

I see people writing things like, "#thanksgivingweekendturkeyblues" even "#BAHAHAHAH"...I just don't get it. You can't click on it, nothing else shows up but some random fragments with no spaces.

WHAT does this MEAN?

[Dhruti]

good question
lol i dont get it either
but i m guessing its something they feel or something that has to do with the status but its not in the status