What's the difference between a headset and a handset? And between a handset and a phone? And...and...?

The handset is the part of the phone that goes in your hand, and includes the parts you listen to and talk into. The plastic shell that holds the parts is the handle.

• If those parts were attached to something that attached to your head 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 (or microphone) and the receiver (or speaker). What some people call receivers, are really handsets.
• Some people even call their entire phone a receiver. Yuck. Some companies call them "voice terminals" or "endpoints." That's ridiculous! They're phones, dammit! .
• Some people, particularly Brits and Aussies, call an entire phone a handset. Double-Yuck (unless it's a cellphone).
• Headphones have miniature speakers (also known as drivers and transducers and receivers and receiver elements) and are mainly used for listening to music. It's unusual to hear the word "headphone." The word almost always has an "s" at the end. It's a contraction for "pair of headphones," like "pants" is short for a "pair of pants" and "scissors is short for "pair of scissors." Headphones are sometimes called cans.
• An earphone is a tiny speaker that fits in or on your ear, commonly used for listening to a portable radio.
• EarPhone® is a tiny ear-mounted speaker with a short microphone boom (sort of a mini headset), made by Jabra for phones.
• EarSet® is an all-in-the-ear speaker/microphone, also made by Jabra. Similar products from other companies are called ear buds.
• HeadPHONE is an advertising label that Panasonic uses for some phones that have headset jacks.