Your car has an intricate network of electrical wires and components. If you are looking to examine a diagram that summarises these electrical features, you'll need to learn how that diagram was meant to be read.
Diagrams, or schematics, for your car's electrical circuits display numerous symbols to represent and explain the paths of wires and the functions of the components to which they connect (i.e. resistors, fuses, switches, etc.). Many of these symbols are repeatedly used and fairly easy to decipher when comparing the diagram to your car.
Diagrams commonly use more than one component and wire path as references to finding your part of interest. For example, when locating a defective horn relay, the diagram may also display the horn and the horn-switch that connects to a ground source. Both of these would be connected to the relay and thus offer separate wire paths to follow and find it.
Some diagrams can include symbols that are difficult to read and understand. Therefore, codes are often included within the diagram to give you component specs and help determine the sizes, colours and amperage loads of wires as well as the pins to which they connect.