Since the caliper only has one piston, the caliper needs to center itself as the pads wear.  The caliper slides on the pins to find the point where it is centered and pressure is being applied on both pads equally.

Be careful washing the rubber parts, do not use anything like mineral spirits as it can swell the rubber parts.  Only use water based cleaners, and if you use products like Simple Green or Purple Power....use them quickly on anything that is rubber and then rinse and dry quickly.

Look stuff over once it is clean....and then decide what needs to be replaced.  Brakes are not anything to try and save money on.  If the parts look worn or aged.....replace them with new.