Timers and delays are used to control the timing of events in your program. Whether you want something to happen after a set amount of time, repeat on a regular interval, or pause execution temporarily, timers are how you manage that.
In everyday programming timers might be used for things like showing a notification for a few seconds before hiding it, or polling for updates every minute. In game development they become even more essential — cooldowns on abilities, enemy spawn intervals, countdown timers, delayed explosions, and frame based movement all rely on timing in some form.
How timers work varies quite a bit across languages and environments. Some languages have built in delay functions that simply pause execution. Others — particularly JavaScript — are asynchronous by nature, meaning delays don't block the rest of the program from running while waiting. Game engines like Unity and LÖVE2D have their own timing systems built in that are worth knowing separately from the base language.