What a light timer does

A light timer turns a light on and off at set times, so a home or shop looks occupied, or so lights follow a daily pattern without anyone touching a switch. A timer outlet is the same idea built into a socket adapter: plug it in, plug the lamp into it, set the schedule.

Programmable and automatic types

A programmable outlet timer lets the buyer set several on and off times. An automatic timer for lights may add a light sensor, so the schedule follows dusk rather than the clock. An astro timer goes further and calculates sunrise and sunset for the location. Each type answers a different need, so the inquiry should name the behaviour wanted.

What to confirm

Ask about load rating, number of programs, battery backup for the clock during a power cut, and whether the schedule survives being unplugged. Those figures are not stated on this site; they are specification questions.