What do @ and # mean on twitter ?

[ayyy sup]

for example on katy perry's twitter
http://twitter.com/KATYPERRY

[Bomb Soldier]

@ = at
# = number

[abcd24]

@ is someones username
such as if you searched for katy perry on twitter, you would search for her as @katyperry

and # is for something called a trending topic, someone will post something such as #newyear , and lots of people may tweet about this, and if this topic is tweeted enough by enough people then it is called a 'trending topic'

Hope this helps

[Shibby]

@ = at user name
# = is used for treading topics (tt). is it also used for searching for stuff on twitter like "#DADT"

[Aryo barzan]

my answer is same to all of em who answered this!

[purringdirt952]

Why is this in "celebrities"?