What do all those counters mean?

We get asked a lot about what the various counter mean in a load test, like requests/sec, response time, tests/sec, etc. 

The counters are documented here: http://msdn2.microsoft.com/en-us/library/ms404656(VS.80).aspx.

Whenever I look for this page, I can't find it because it is not in the most intuitive place in the TOC, and for some reason the search engines don't return it when I search for specific counter names.