From ROI Wiki

The name "Controllers" is a nickname, used by the residents of the planet of Offworld, to denote or identify either Section 17, the Alien Brotherhood, or the combination of the two, known as The Syndicate. It's also used as a more generic term meant to refer to anyone who is responsible for controlling what happens on the planet of Offworld, and thus doesn't always have to refer to the Syndicate, or its two component parts, although that is its primary use.