In much the same way that the Filename Template Editor is used to process the names of files being moved to the media library so Filename Processors is used to inform TV Rename what filenames to look out for when searching for a missing files
To really understand the contents of the Regex column above, you need a working knowledge of Regular Expressions.
Once you have figured out whats going on you can see that all the regular expressions capture the season and episode number of a show from the filename. Each one can work on just the filename: -
or on the whole path: -
The expressions are evaluated in order (top down).
Each expression can be toggled on and off, as can the ability to process a full path.
Each expression has a Notes field which can be used to remind the user why the expression was added.
Additionally, a folder can be specified to test the results of the Regular Expression.
If a match is found during the test the matching expression is indicated.
In all likelihood you will find it unnecessary to make changes here, only if a new, totally unrecognisable file name structure appeared would it be necessary, and then there would probably be discussion about it in the forum.