Quoted from ForceFlow:

http://www.lawmart.com/forms/difference.htm
Generic parts (like the button) or mechanisms are typically patented, not copyrighted or trademarked. However, once the patent runs out, anybody can make generics. Parts with artwork on them (plastics, backglasses, playfields, etc) retain copyright protection because of the artwork that is on them. Parts with specific color schemes and/or logos typically carry trademark protection because of the logos and/or recognizable color schemes (e.g., flippers with the Williams "W" logo, or flippers with the Gottlieb name stamped on them).
[edit]: In short:
Patents protect inventions, objects, or mechanisms that can be manufactured. They also can protect a process or method that results in something being produced. The patent holder has exclusive rights to produce the said items until the patent expires (however, there are exceptions if an inventor refines/updates an invention and applies for a new patent for it)
Copyright protects creative or published works, like artwork, written works, books, articles, music, drawings, paintings, sound effects, voice recordings, etc.
Trademarks protect the use of a company's name, logo, or any recognizable attributes which makes them unique or identifiable.
Post edited by ForceFlow: added summary of differences