What's with the "#..." on twitter?

[Wout]

I don't get this. I'm really not into Twitter, but when I see someone's Twitter page, there are all these blue words after the #...What's the meaning or does it have any purpose?

[Malia Rimmer]

It'll be a topic that's trying to be a trending topic.

[gmcblaze106]

it means if you see a word with the # you can search it and see all connected tweets with the same word.... it only really works with well trending words or topics, but sum people just do it with dumb words to look cool

[succubus]

It's a tag, they call it a hash tag. you tag your "tweets" with this in order to include them in a category. people can search by these tags to find messages related to a certain topic.
when a lot of tweets with that tag are being written the tag starts "trending" and appears on your twitter main page