Hi Robin, It is a very complex and frustrating task to understand it all. I started little over a year ago, and I was ripping my hair out then. Sometimes still do. It's so much that I can't even begin here to try and explain. Please join this team, CindyLou is the queen of SEO:
CindyLouWho team
There are other great sellers who also know this stuff inside and out, maybe they will pop in.