Does that mean "Furnished apartment is highly appreciated"?
This is the core of it:
This phrase is used by people who are looking for a place to rent, say a room in a flat sharing, or a small apartment or so, typically students, or people who start working in another city and need a quick solution for living. They use this sentence in order to clarify that they would accept both an empty room (or appartment) and one that has furniture.
It is not to indicate a preference. It indicates that both is acceptable.