Why do people put # at the start of some words, especially on twitter and youtube?

[fatarm696]

Occasionally at the end of posts I see people put the hash symbol (#), especially on Twitter and Youtube. For example someone might put 'Osama bin Laden is dead. #good' or something... why?

[jesssavage]

it is to tag things in your post
like on facebook how you put @ before someone's name and you can tag them

[Aleneen O]

For twitter, it is a kind of a topic indicator. Once posted, the # and the first word connected to it become a link. When clicked, you are directed to a list with other recent posts that contained that same word with a hash.

On YouTube, I've mostly seen @. @ stands for 'at', when directing your post at a person. For youtube, this is used when replying to someone else's comment in the comment section of a video. On twitter, this is to direct your post to a fellow twitter user, usually as a reaction.

[Mia F]

It refers to a link, or something, some news..and it is NOT good when some1 is dead! ok just kidding.

[Obscure Hollow]

I don't understand it completely, but I tried to search through an #something and in a website I saw the "trend" of the twits.
It's mabye userful to "filter" all the twits that are talking of an argument.
for example, if I talk about Forrest Gump and I write #Ilovetorunfast that tag maybe is been used from another user, while he was writing: I was so scared from that wild animal #Ilovetorunfast
Then, you search that hashtag and you will find those 2 tweets.
It's a way to be found by people you like, or to find someone who likes your same things.