What is that thing with the # on twitter?... Also, how do you "retweet"?

[Natalie Johnson]

I don't get it? Are they just putting a # by random words to make them red?

[rhian palacio]

The # sign on twitter is a trending topic or a team. RT or retweet you just click on the arrows that are on the tweet that someone wrote

[Payel Biswas]

ITS CALLED TRENDING.
its like #(a phrase or words that people want to get popular on twitter).
like #harrypotter or something like that, so it'll appear on the 'trending' page so that any tweet which mentions that phrase / word with the # will appear there.
hope you get what im trying to say.

you copy the message, then hit the reply arrow next to the message so you'll have the user ID, then paste the message and type RT at the beginning of the message.
for example if you want to retweet a message I sentthat says "Twitter rocks" it will look like "RT @Huayruro Twitter rocks"