The controllers energizes the remote control valves that operate the sprinklers or the irrigation system, according to the program you set. Basically it is an automatic timer which runs a pre-set program that regulates when and how long the sprinkler or the irrigation system should run. The program dictates which days of the week, the time of day and total run time, the irrigation system will run.
When the controllers is initially set up, you must first program the current time and the day of the week. All irrigation controllers need at least three elements to produce a working program: start time, days of the week to start, and run time for each station.