The hot wire to the fan in a fan/light kit will usually be black and the light wire will be blue. The white wire is usually the neutral which is always connected directly to the source neutral, either at the source or through a splice in the switch box. The white wire may also be used to carry current when necessary.
In this wiring, the source is at the switch and 3-wire cable runs from there to the fan/light. The switch controls the light and the source is spliced through to the fan. With this arrangement, the fan is controlled by a pull-chain on the motor housing and the light is controlled with the switch. The neutral and ground wires are also spliced through to the fan/light.
This page contains wiring diagrams for a ground fault circuit interrupter (gfci) with a built in switch. This device can be used to protect a garbage disposal and provide a gfci protected receptacle in a single gang outlet box. The switch can be included in the protected circuit or it can be used to control an unprotected light or other fixture.
This is the updated wiring for this arrangement, with a 2-wire cable added between the fan/light and switches. The white wire is no longer used for hot and the source neutral is run through to the switch box to satisfy the 2011 NEC requirement of a neutral wire in all switch boxes. All other wiring is the same as above.