Hey Goldie,
The @ symbol is for when you're talk AT someone or sending a message @GmaGoldie(directly to an individual).
The # symbol is a HashTag and when you use it on Twitter it's telling other people that you are/have sent a tweet that goes under the Topic Heading of whatever #HashTag you use. (ie #Forums #Talking #Chat #History and so on)
In the forums, if a person is using forum decorum, then when they reply to a specific post then they are talking to that specific individual. If they just post a reply then they are talking to the OP or making a generalized statement.
You can use the @ symbol in the forums to direct a question or statement or reply directly to someone, it's done all the time, but it's not necessary if that person is taking or posting to the forum thread.
I hope that helps.