what does it mean when people use the symbol # before a word?

[Jason]

i know it means number but why is it used before words. the T.V show "Workaholics" uses it. they put it in the bottom left corner of the screen #Workaholics
So if it is Twitter feed then when people are using it on facebook and just other random things, they are all talking about Twitter too?

[Nakil Cole]

Yep this # infront of words is called a hashtag a topic in a more simpler term on Internet usually twitter but people use it on Facebook and other social networking sites when people use it other places besides twitter its a topic on that site alone possibly on twitter too but mainly on that site Let's say I'm upset ill put as my status on FB "I hate school!!#imupset" I'll put it so other people who are also upset can use it then it becomes a trending topic