OLT Configurations, Metric Profiles and Metrics?

This question is about Oracle Load Testing (OLT)

Can someone explain the difference among, and the relationship of Configurations, Metric Profiles and Metrics?  The OLT User Guide just tells how to create them.  Not what they really are.

I'm trying to define different kinds of servers for our organization that I can use in future load tests, without having to recreate them every time.  I have a specific set of metrics I measure for an "Application Server", a "Web Server" and a "DB Server".  And these are different from the predefined sets that come with OLT.  Most of the metrics are gathered form perfmon.  But, I think I'd like to include some of the Apache or Oracle stats OLT can collect.