Final answer:
An encroachment is the unauthorized intrusion of Joe's building onto Ginny's land, distinct from an easement, which is a legally permitted use of land.
Step-by-step explanation:
The situation described where a portion of Joe's building was inadvertently built on Ginny's land is called an encroachment.
This happens when there's an intrusion on a person's territory or property. Unlike an easement, which is a legal right to use someone else's land for a specific purpose, encroachment usually occurs without proper authorization and typically needs to be resolved through removal of the intrusive structure or through legal agreements between the property owners.