Yes, your valves (master and/or zone) are likely below ground. They would be buried in some type of round or square box with a plastic lid that can be removed to access the valve.
If you can find the valve, you can manually open it by turning it to see if that turns your sprinklers on. If it does, that means the controller is not turning on the valve for some reason. It could be an issue with the wiring between the two or the valve itself may not be responding to the electronic command. In either case, you could water the yard by manually opening the valve until it is fixed.
If you manually open the zone valve, and the sprinklers don't start, it means you have an issue with the water flow upstream of the valve. It could be at your master valve if you have one (similar to the zone valve issue described above) or could be farther upstream such as at the PVB (bell-shaped metal piece with pipes and valves that sticks up out of the ground - likely near the house).