Imagine there are two balls, a red and a blue. You want to communicate to your friend rolling the only blue ball to them. In a ferromagnet there are only blue balls, in an antiferromagnet the blue and red balls are glued together and in an altermagnet there are both balls but they go in different directions so you just need to orient yourself correctly.

The antiferromagnet can't be used for spintronics, the ferromagnet can but big magnetic field disturb other parts in a circuit.