This wiring arrangement allows for lowering the lights with a dimmer and controlling the fan with the builtin pull chain. The source is at the ceiling outlet box and 3-wire cable runs from there to the switch box. The neutral from the source is spliced directly to the white wire on the fan kit and the cable, running it through to the switch box.
This page contains wiring diagrams for two outlets in one box. Included are arrangements for 2 receptacles in one box, a switch and receptacle outlet in one box, and 2 switches in the same box. In this diagram, two duplex receptacle outlets are wired using pigtails spliced to connect the terminals of each to the source wires.
The white wire is wrapped with black tape to identify it as hot. The black wire connects the fan to the speed controller. The red wire connects the light to the dimmer.
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.