Comments page — any info on how to use this?

First there is a checkbox in front of Author. What does checking that do?

Also, how do you select a particular comment for an action, or do you have to chose a single action for all comments? Either approve them all, unapprove them them all, …. doesn’t make sense.

The book I bought tells me nothing about this and searching the web was useless as well. Anyone have a useful link?