A Partition Wall is simply any wall of a house that separates rooms - it does not separate the inside of a building from the outside. It is unlikely to be a load-bearing wall. It can be constructed using a number of materials including:
Why Create a Wall Partition?
People install a new Wall Partition to create two, or more, rooms out of an existing one. Perhaps they would like a quiet study room for their child, or an en-suite bathroom attached to their bedroom.
A Partition Wall does not have to entirely divide two parts of a room into new rooms - it can be built to just partially divide a room.
If you are considering creating a Partition Wall then it is best to have a Surveyor take a look at the room and your proposals, to see what the best way to proceed is.