feedburner is where you burn feeds . join , put your url in the tool it will give you a feed address , this is how people that use feed readers such as atom or rss read the new content posted around the net, go through the steps to set up auto ping and email subscription and all the other stuff . it makes it much easier to get traffic to your blog and you can see how many have subscribed or just read your feed . if you then join twitterfeed you can automatically post to facebook twitter and status net without leaving your blog . theres more to it but thats about the bones of it .
Feed burner is a service provider offering RSS feed management. A few years back, Google took over feed burner and now is called Google feedburner