I still actually have no idea how twitter works - I've tried it a few times to follow some of the motorsport guys but it still confuses me!
You follow people. People follow you. People you follow tweets appear on your newsfeed. You can retweet their tweets and then they appear on your followers newsfeed as you retweeting them. You can mention someone in a tweet by putting @*insert their twitter name here*. Hashtagging allows lots of tweets to be grouped together. So if you #RsMegane in a tweet, you can search for that hashtag and see anyones tweets that have ever used that hashtag.
It is. I've been on there for ages and have only one follower (the wife). If it weren't so shit I'd get rid like I did with facebook.