so anyone good at twitter?

can anyone tell me how people that are not on my friends list are able to retweet my messages?

I thought only people on my list could see what I tweet

Your followers are more likely to retweet your stuff because they are more likely to see it since it is in their timeline when they log in to twitter. However, anyone can retweet your tweets, they don't have to follow you.

Try this - click on one of those twitter accounts they suggest you follow and see their tweets. You can retweet any of them if you want.

Anyone who Follows you can see your Tweets in their timeline and reply to them. They don't even have to follow you though, you can just search for a name and them message anyone you want. You can not Direct Message (D someone who you are not mutual followers with.
If you really want to get into it try using Tweetdeck.

I Wish i was Good at using Twitter too! I dont use my twitter Nearly enough as it is! =)