Can someone explain twitter hash tags to me?

[Guy]

[Maddy]

When people are frequently talking about something like.. Glee for example they type #Glee somewhere in their tweet. People can click on the hashtag or type it into the search box on Twitter and see how many other people are talking about it as well.
I was confused too

[Kelcey]

A hashtag # is what's trending/already been trended so for example "I'm am so #Tired I need some #Sleep see what I mean? Hope it helped

[Banker Zero]

What everyone is saying here is correct. I like to conceptualize it another way though. Ever been in an online/AOL chatroom? Well if you have, think of it like that... by tagging your tweet with #glee, you are tweeting in the twitter "glee" chatroom. this is especially true with real time discussions about a TV show, etc.

Some news outlets will use hashtags to get user feedback and post that feedback on live TV (CNN and MSNBC both do this).

If you're Mitt Romney, you might pay $120k to promote your hashtag #RomneyRyan2012, IF you're Kal Penn Speaking at the DNC, you might get #sexyface to "trend" for FREE for TWO DAYS just by mentioning it in passing during your speech.

Bill Clinton just needs to speak at the DNC for Monica Lewinsky to trend.