The wiring in this diagram is for adding a new light fixture to a switched receptacle, i.e. one that is hot only when a switch is on. These are commonly used to turn a table or floor lamp on and off from a wall switch.
This page contains wiring diagrams for a service panel breaker box and circuit breakers including: 15amp, 20amp, 30amp and 50amp, as well as a GFCI breaker and an isolated ground circuit.
Back at the source, the white neutral wire is spliced to the white from the fixture cable and to a pigtail, back to the receptacle neutral terminal. At the fixture the white connects to the neutral terminal on the light. The hot terminal on the light is connected to the red wire from the switch loop cable and the other end is connected to the top terminal on the switch.
This page contains diagrams to add a new electrical outlet to an existing circuit. Arrangements are included to use an existing receptacle circuit or lights and switch circuits as the source for a new wall outlet.