What does putting '#' in front of a phrase mean on Twitter?

[Song Billong]

This might be a stupid question, I'm not sure. I'm quite new to Twitter!

I noticed that it highlights and underlines the word/phrase and creates a link to the search results, but what's the point of it?

[Jess]

To see who else is discussing that same topic. When you click it will search Twitter to show other users who has interest in that particular topic.

Some people make up their own hashtags like #hateworkingherewanttogohome which is probably not going to link to anything, however using #grammynominations or #grammy will most likely link you to relevant topics.

[eepitswill]

It puts a link to what other people put after their # too. Its called hash-tagging.