when do you use the "#" on twitter?

[Brooke.an]

im new to twitter, and sometimes there are trending topics that have "#" and also in people tweets. im just wondering? lol

[Jasmine]

I think it's when you're referring to a topic. Like #music.
That's why in the trending topics you may see #musicmonday or #playing now.

If this doesn't help, google it. Theres a few answers on there.

[~Puppi~]

most people in my twitter feed use the "#" to make certain topics they are talking about trend. that's all i've seen it used for.