These tabs are created when you load a character by clicking on either the New or Import buttons. Each tab gives you a view of certain attributes of your character put into logical groupings. In some cases the selections in one tab (like the Constitution score in the Stats tab) will affect data in another tab (like the HP field in the Classes tab). The tab's name will reflect the name of the character. This can be changed by editing the value in the Name: text field at the top of the window.
The tabs that make up the character info pages are: Stats, Classes, Abilities, Skills, Feats, Domains, Spells, Profile, Traits, Misc, Equipment, Companions and Preview