Spiral and planetary mixers can often be confused for one another. There are key differences to look for however.
Planetary Mixers are the more common type and are probably what pops into your head when you think about large floor model mixers. They have fixed bowls that are latched onto the base of the machine and are raised to the proper height for mixing by a lever. They do come in different models and sizes that are suited for the counter top or floor. Generally planetary mixers also have variable speeds that compliment their attachments, such as paddles, whips, and dough hooks.
Spiral Mixers differ from planetary mixers in a major way. They have rotating bowls or mixing compartments. This enables delicate dough to be mixed but not overworked or overkneaded. It also helps create a more uniform and homogeneous mix. Spiral mixers are great for gluten development in dough because of how gently they combine ingredients.
Many spiral mixer manufacturers also have built in the ability for the bowl and base to detach from the rest of the machine for easy transportation.