Removable braces are usually worn only on your upper teeth. They are kept in by metal clips that fit over the teeth at the front and back.
Removable appliances have an acrylic base and stainless steel components to hold the appliance firmly onto the teeth. Movement of teeth is achieved by the stainless steel springs being distorted out of shape during activation by the dentist, so that as they move back to their original shape, they pull or push the misaligned teeth with them.
How is it done?