Quite a lot actually. We all use names to identify ourselves from one another and the SCA is no different. The exception is that we try to use ‘personas’, a type of free-form acting part (self scripted) to distinguish our SCA activities from those of our ‘real’ lives. Names once selected can be registered with the SCA College of Arms, post scrutiny, to ensure your right to sole use of that name.
You begin with a ‘given name’ such as John, Paul George or Ringo, which is usually followed by one of the following. A vocational name (Bob the blacksmith), a locational (…of Glen Rathlin) or even plain descriptive (Olwyn the Ugly!!), later periods introduce the concept of family names (d’Audrieu), the choice is up to you.
More details from the link above ‘Naming 101’ or from the general links