What are luggage bags

Pannier bags: Bags that are mounted on the bike's pannier rack or can be attached to it with quick-release fasteners. Usually attached to the side of the pannier rack. However, other, usually smaller versions for the pannier rack are also available.

Luggage bags (also pannier bags):
 Bags that are mounted on the bike's luggage rack or can be attached to it with quick-release fasteners. Usually attached to the side of the luggage rack. However, other, usually smaller versions for the luggage rack are also available.

Relevant articles:
Luggage bags from HiLo sports