Blogger: This term is used in two different ways. It can mean any person who publishes content to a blog or it can refer to Google's blog service, Blogger. When referring to Google's Blogger site, the "B" is usually capitalized; when talking about someone who posts content to a blog, the "b" is not necessarily capitalized. eg blogger, I have a blog- Im blogging on it right now.

Blogosphere: Generally, this encompasses all the blogs (commercial, personal, etc.) in the blogging community. The world of blogs is a loose translation

Blogroll: This refers to a list of links to other blogs that the author(blogger) of a blog also read regularly. The blogroll is usually located on the sidebar on the blog page. So if you like what you are reading, you mightwant to check out some other blogs that might also interest you and "blogroll" them too.

Hopefully- you will also get people doing this to your blog- and surfers clicking through to your blog too from someone elses blogroll.
_______________