LSL Wiki : parcel

Parcel

A parcel is a block, or "lot", of land in a sim with a minimum size of 4x4m, not necessarily contiguous (connected), and can be split and joined with other parcels of the same owner (but may not cross a into another sim).

Q: Is there a way to determine how large a parcel is, or if another object or agent is on that parcel?
A: No, but you can find out if an object or agent is over an owner's land using llOverMyLand or llGetLandOwnerAt (assuming you know the position of the target object).

A2: If you own the land, you can find out who has objects on it by right-clicking anywhere on your land, clicking on the object's tab, and hitting the refresh button near the bottom.

Land | Simulator