The little plastic tips on the ends of cords and cables are plugs. Plugs fit into jacks. Despite their male name, jacks are female. Plugs are male. If you don't understand this, find someone of the opposite sex, get naked, and look in the mirror. Or study Michelangelo's "Temptation and Fall" on the Sistine Chapel ceiling in Rome.
Modular plugs are made in four standard sizes:
The smallest plug, known as 4-position/2-wire, is used for handset cords.
The middle-size plug is the most common. It has six positions, and either two, four, or six wires. It is used for most line cords, for connecting phones and other devices to phone jacks.
- The largest common plug, with eight positions and eight wires, is usually used for LANs (Local Area Networks) and sometimes for phones.
There is also a jumbo plug with ten positions and ten wires used for specialized applications, but probably not phones.
(above) The AT&T Merlin is one of very few phones that used the wide 8-wire plug and jack. Most modern phones (below), even those handling dozens or hundreds of phone lines, use 2 or 4 wires with narrower plugs.