This type of circuit is called an earth-return system any part of it connected to the car body is said to be earthed.
The fuses are usually grouped in a box or on a panel with a cover. Ideally, the box should be fixed in an accessible place — such as the bulkhead under the bonnet.
The other, probably rated at about 20-30 amps, protects components not wired through the ignition — horns, interior lights and the cigarette lighter. Where a single fuse protects a number of circuits and keeps blowing, each circuit must be checked individually to discover which one is faulty.
The electrical system of a car is a closed circuit with an independent power source the battery. It operates on a small fraction of the power of a household circuit.