It seems to me that the important thing about an objective morality or ethical system is that it is independent of the desires and choices that people make. Instead of it being something we create, it exists in some way independent of us.

An objective morality might come from god or from the nature of things, but it is there for us to discover. It isn't something we create based on our feelings. For example, if killing is objectively wrong, then it is wrong even if we don't think so.

I'm not so sure about how we should define absolute. Sometimes I think absolute means "without exception" in this context. For example, if we said that it is absolutely wrong to lie it means that it is always wrong - no exceptions.