Some of the jargon used in the world of blogging can be a little confusing. So I’ll try to explain it with a story.
Derek, the webmaster, has an account. He also “owns” a blog. That is, he’s the Editor of the webmaster blog. If Derek gets hit by a bus and we hire a new webmaster, the new webmaster could get an account and take over Editor duties on the webmaster blog. The purpose of that blog is to provide a communication platform for the College webmaster, not to provide Derek a place to discuss his political leanings or religious views. Derek has other places on the internet for that sort of thing.
Mary also has an account. She is the Editor of the Educational Technology blog. The purpose of her blog is to discuss educational applications of technology. After having a conversation with Derek, she decides to invite him to write a guest post on her educational technology blog.
Mary trusts Derek to not do anything stupid or illegal on a blog she’s ultimately responsible for, so she asked the Administrator to add Derek to her blog as an Author. If Derek were added as a Contributor instead, Mary would have to approve anything he wrote before it gets published.
Derek is now an Author on the educational technology blog. He is still Editor of the webmaster blog. When he logs in to his account, he can go to the dashboard of either blog and find tools tailored to his role for that blog. Since Derek is an Author on the educational technology blog, anything he posts will be published immediately. But he can’t access or edit Mary’s posts. However, as Editor, Mary can edit or even delete Derek’s posts on her blog.