good algae vs. bad algae

You'll have to excuse me folks. I think I've established the fact that I'm a noob, but I've really been reading a lot of information on this site...but I'm still a little confused.

This paticular board seems to be about the algae you don't want in your tank. I've read things about some kind of algae seeding too...so, what gives? Do I want algae on the back wall of my tank (...and how does one contain it to that wall?) or algae is ok if there's something to eat it?

 

Here's basic Algae 101 for a reef tank:

Green/hair algae: Good/acceptable in a new/cycling tank but bad otherwise

Brown/diatom algae: Good in a cycling tank. Bad, but acceptable in limited amounts in an established tank.

Coralline algae: Very good but a PITA to scrape off the glass

Hope this helps

 

Thanks!