The panel should also have a ground buss bar where all the branch ground wires screw in. In main service panels, the ground buss and neutral buss are connected together to provide a safe grounding path for both busses. All newer homes, and many older ones that have been re-wired, will have circuit breakers. Each breaker controls the power to a group of lights, outlets and appliances. If it hasn't been done already, you should label each breaker so you know just what it controls.
Circuit breakers protect the wiring and fixtures by turning off the power.
That cuts power to the circuit and protect the wires and fixtures from damage. The most common reason for a breaker to trip is too many appliances and lights on one circuit. A tripped breaker usually looks like it's between the ON and OFF positions. To reset a breaker, turn it OFF and then ON again. If a service panel doesn't have breakers, it probably has fuses.