Apache's new contributor documentation and Maven's glossary are great places to start if you are new to Apache or Maven.
Module
Almost the same meaning as "sub-project" on Maven.
Personality
A chunk of shell code that tells test-patch this particular project's needs and special requirements
Plug-ins
Shell code snippets that define new, not built-in test types.
Precommit
An automated process that verifies a patch is "good" prior to a committer looking at it.