Help for using the QA/QC Tool can be found here:
Help on configuring the QA/QC Rules can be found here:
I found how to configure the rules, but how can I know what is the meaning of each rule?
Where I can read about the different rules?
A lot of the messages are usually related to domain or connectivity violations. Sometimes these can be a little cryptic but you can usually work out what the issue is.
There is also a list of out-of-the-box validation rules here ...
It is also possible that your site has custom validation rules. In this case the messages would be up to the developer.
Perhaps you could post a few of the messages or rules you want more information on.