Please explain this thing on twitter to me?

[♥♪♫♥]

I get it, but I don't understand what it mean when someone tweets something and then beside it there is a link to somenting like #something.
Is that a page they are posting to or something?

[V3R0N1C4]

I was confused about twitter once but then I dove in head first and started learning by myself. Ok those #hashtags you are talking about are sort of a category link. When I tweet something about my favorite song perhaps
this is my tweet---> "My Love is Like A Star"~ I love @ddlovato #GoodMusic ----
By putting the hashtag I categorize the tweet for when people search "goodmusic" or "music" on twitter. It shows up to them. Hope I helped.