A keycap is a small plastic cover placed over the keyswitch

Keyswitch

*A keyswitch is a type of small switch used for keys on keyboards. These are now largely out of use due to most modern keyboards using sheets of plastic with contacts on them...

 of a computer keyboard

Computer keyboard

In computing, a keyboard is a typewriter-style keyboard, which uses an arrangement of buttons or keys, to act as mechanical levers or electronic switches...

. Keycaps are illustrated to indicate the key function or alphanumeric

Alphanumeric

Alphanumeric is a combination of alphabetic and numeric characters, and is used to describe the collection of Latin letters and Arabic digits or a text constructed from this collection. There are either 36 or 62 alphanumeric characters. The alphanumeric character set consists of the numbers 0 to...

 character they correspond to. Early keyboards were manufactured with the keyswitch and keycap integrated in one unit; separate keycaps were introduced to facilitate the production of different keyboard layout

Keyboard layout

A keyboard layout is any specific mechanical, visual, or functional arrangement of the keys, legends, or key–meaning associations of a computer, typewriter, or other typographic keyboard....

s.

Typical keycaps of the 1970s and 1980s were produced using 2-shot molding, with the markings molded into each keycap in a different color of plastic, but this eventually fell out of favor, as it was more expensive (particularly in tooling costs), and tended to produce keycaps more durable than the equipment on which they were mounted.