For an inflatable board it makes sense to buy a paddle that can be split in 3 pieces so it fits in the bag that comes with the board.
What is meant is that the shaft (the pole which you hold) is made from aluminium. This is the most affordable option and to be honest is perfectly fine to learn to paddle.
What is meant is that the shaft nowis made from carbon. Carbon is lighter then aluminium, resulting in less swing-weight. Also the handle and the blade can be made from carbon. Finally carbon paddles are expressed in the amount of carbon. If a paddle is 100% carbon it means shaft, handle and blade are made from it.
These paddles come with an extra blade that can replace the included SUP handle piece, and so form a canu paddle.