What is 'aquaplaning' (or hidroplaneo) and what is the proper action if your vehicle experiences it?

1. Tires grip the road better in heavy rain; accelerate to push through the water
2. Tires lose contact with the road surface by riding on a film of water; gently ease off the accelerator without braking abruptly or making sharp steering movements
3. The car's cooling system overheats; pull over immediately and turn off the engine
4. The brake pads dry out; pump the brake pedal vigorously and turn the wheel sharply