The word hurricane is the name given to natures strongest storm.
A hurricane occurs when high pressure and low pressure masses of air come in contact with one another.

There is often a significant difference in temperature between the two masses.
One mass is warm, while the other is cold.
The warmer air rises, and the cooler air falls.
Likewise, the low pressure area slides down the sides of the high pressure area.

They swirl in and around one another, creating the beginnings of the storm.