This post by Stymiee was made on the Sitepoint forums some time ago, but it’s always worth revisiting. The basics of Search Engines in FAQ style.
Sure, it doesn’t cover everything, but there is quite a deal of knowledge here – including dispelling a few common myths.
Although the author makes a bit of a disclaimer:
Since SEO is not a science this is a gutsy post to make so cut me some slack!
I’ll cut you some slack Stymiee – it’s a great post!