Learning how to read wiring diagrams is possible through books, magazines or websites dealing with basic electronics or physics. It is also possible to learn how to read them from a class on electronics or an experienced electrician.
Wiring diagrams explain how the circuit for a particular set of wiring works. Makezine.com explains that they allow the reader to understand how the flow of electricity in wiring works, without needing to understand the exact details of the circuit. It is important to understand how to read them in order to work safely with electrical devices, such as in the building of small electronics or repair of appliances.