Why do people use the numeral sign while posting on facebook and twitter etc?

[Alexis]

I see people randomly using the numeral sign # next to a post. Also, in the memos for my work at the title of things they would have a # sign at the end such as "September Guidelines #". So why do ppl throw that # in??

[bubblegum32197]

it's a hashtag. basically when you put a hashtag next to something it's a keyword in whatever you're posting. so if someone makes a search with those keywords your post will pop up

[anon....ha ha]

I know this isnt particulary helpful but i know now people use it in speech as well they would say 'hash tag______' and then the rest of the senctence ...makes no sence to me xx