Some people call phones handsets , which is not very pompous, but is even more confusing. The handset is the part of the phone that goes in your hand, and includes the parts you listen to and talk into. If those parts were attached to something that attached to your head or your ear instead of being held in your hand, it would be called a headset , instead of a handset. The important components inside a headset or handset are the transmitter and the receiver . What some people call receivers, are really handsets.
Some people even call their entire phone a receiver.
When you pick up the handset, you go off-hook . When you hang up, you go on-hook . A lot of our current telecom vocabulary is based on the parts of ancient phones, like the candlestick above. Some phones have buttons labeled flash and some fax machines have hook buttons.