A fixed panel encloses one side of an already-roofed space (like a canopy) - it's an add-on, not a standalone room.
A sunroom is a complete, fully enclosed and glazed room in its own right, usable as genuine indoor floor space year-round.
The simple test
If you already have a roof and want to block wind/rain from one side, you need fixed panels. If you want a genuine new room, you need a sunroom.