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 now is made from carbon. Carbon is lighter then aluminium, resulting in less swing-weight. Also the handle can be made from carbon.
These paddles come with a blade which is also made from carbon. These are the lightest paddles.