Note the many different types of filters you can create.
Accept List Filter is a "white" list. You can use this to say "accept all main from this person or this domain"
(A domain is everything after the @ sign.)
A block list is a "black" list. You can use this to say "deny all main from this person or domain.
A mailing list filter is used for mailing lists you might be on. This is helpful to funnel this mail into a particular folder.
And of course, custom filters are just that. You can use that to create any type of filter.