What does the # in Twitter mean?

[Jessica]

When someone posts something like(USING THE SHOW THE VOICE AS AN EXAMPLE!) #the voice... what does the # mean?

[Gladius]

Putting a # before a word makes it a "hash tag", which is sort of like a topic for the message. So a more normal example would be something like "Wow! What #Romney said was really stupid, he'll lose for sure now." And then anyone looking for tweets about Romney can find it easily. Sometimes people use it just to be funny though.