Once you have contacts segmented, you can add them to groups by using the advanced search. Say you want to make a group called Universities so you can easily contact everyone who works at a Uni. You can use the advanced search and find all "Subscriber Types" and add them to a group. Now you can click the group and see everyone at a Uni. When more contacts register, you can "refresh" the group and anyone who submitted after you made the group, will now be added.