A rule in Magic Launch defines a set of criteria that decide whether or not to open a file with a particular application.
You can create a rule for any file type. The rule’s criteria will be evaluated when opening a file of this type. If the criteria matches the file, the file will open with the application specified by the rule.
If a rule’s criteria doesn't match the file, other rules will be evaluated. If no other rule criteria match the file, then the file will open with the default application.