This is a table that holds regular expressions (regex) to include or exclude objects from alerts.  The table columns and definitions are as follows:
Column DataType Comment
InstanceID bigint InstanceID for the server being configured.  The InstanceID comes from the server's entry in the dbo.Servers table.
Action varchar(10) Values: Include|Exclude.  This is the action that you want to take against this regex.  Do you want to use this row to include the results in the alert, or to exclude them?
Module varchar(50) Which alert or module do you want to apply this row to?
IsActive bit You can turn rows on/off with this setting without losing the definition itself.
Comment varchar(500) Tell yourself and others why this row exists.  It'll help everyone if you document the reason.

Each alert allows you to include or exclude objects using regex.  It should be noted though that some alerts will only allow exclude operations as they're the only ones appropriate.  For example, the New/RetiredDBs alert.  You can exclude all DBs that end in the word 'Test' because these DBs may come and go all the time from your server and there's just not point in alerting on them all the time.  But to only include specific DBs would defeat the purpose of the alert itself as it's meant to tell you when DBs come and go so you can be made aware of it in case you need to request more backup space or other resources. 
In fact, you'll probably find that there may not be any alerts that support the Include action type.

Supported Modules:

CheckDB
Backup
NewRetiredDBs