Why burglary? Why not armed robbery?
Aggravated burglary = illegally entering a dwelling while armed with a deadly weapon (or words to that effect). It's like armed robbery + breaking and entering, sort of. Some states have supplemented that with "home invasion" charges, which just adds a "dwelling was occupied" element to the burglary.
Armed robbery would be a more applicable charge if the victim were accosted and threatened while out on the street, basically anywhere outside their house or apartment.