We often use removable appliances as a first stage in treatment, before going on to fixed appliances. Despite the name, they are intended to be worn all the time! The appliance in the top pictures is being used to expand the patient’s arch to make space for the unerupted teeth. It does this with a small screw device in the palate which the patient opens a small amount every week with a special key.
The appliances in the lower pictures are “twin blocks”, which are separate upper and lower braces which are being used to bring the lower teeth forward and correct the discrepancy between upper and lower teeth.