Long before we had GPS (Global Positioning System) devices, people used a magnetic instrument called a compass for navigation. Some people still use a compass to navigate — usually when their GPS isn’t working.
Compass can also refer to another type of instrument, one that’s used for drawing circles; this should be familiar to you if you have ever studied geometry. In addition, compass can mean "range" or "scope." If you decide to hike the Appalachian Trail, using a compass (the navigational kind) should hopefully fall within your compass of ability. If not, we hope you own a reliable GPS.