Right so i get the @joebloggs it is to pin point someone, kinda like a twitter email address, 1 question is if i "tweet" someone using their @joebloggs is it private or does everyone see it.
The #tag and trend then, if i have this right a trend is just a general word that comes up on peoples tweets if they all happen to say it, when you get a #tag it is a way to make a word but more likely a phrase trend such as #comeonyesaints, people would know i wanted them to use this phrase/#tag