First of all, let’s understand the two terms separately. Relays are electrically or electromechanically powered switches that control circuits. The relays can open or close circuits depending on the need. Timers as the name suggests is a device to set time preferences. The timer helps when a function needs to be carried on for a specific time or needs to be delayed. Relay timers combine the properties of these two and make an important part of various applications. The device is used in various households as well as industrial machines.