how do microwaves work?

Question

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Answer 1

Microwaves are very-high-frequency radio waves that swing back and forth at a frequency of about 2 billion cycles per second. During this process, they make certain molecules move, and once they're moving, they're hot. Microwaves enter food from the outside, and penetrate instantly into a chunk of food, heating and cooking as they go.

Answer 2

Microwaves are used in several places, for instance in radar and at home in a microwave oven where the microwaves are used to heat the water in food.

Water molecules are tiny electric dipoles, meaning that they have a positive charge at one end and a negative charge at the other.
In a micowave oven the dipoles rotate as they try to align themselves with the electric field induced by the microwave beam.
This movement creates heat as the rotating molecules hit other molecules and put them into motion too. Microwave heating is most efficient on liquid water, and much less so on fats and sugars (which have much smaller dipoles), and frozen water (where the molecules are not free to rotate).