A hurricane (also called a typhoon or a cyclone) is basically a huge wind. Hurricanes form in the summer and especially in the fall, because they can only form where there is cold air high over warm ocean water. Hurricanes form near the equator, because that's the only place where ocean water gets warm enough. But they don't form right at the equator, because the earth's rotation is what gets the wind spinning around, and it doesn't cause spinning right at the equator.
When the ocean is warm, the water heats the air right over the ocean, and some of the ocean's water evaporates into the air. This warm, wet air rises, because hot air rises. It makes thick, heavy clouds. The warm air rising pushes cold air higher up out sideways. If another wind is blowing on the rising warm air from the side, it can begin to spin around and around, picking up more and more air and water - that's when it starts to be a hurricane.
As long as the hurricane stays out in the ocean, usually it's not much of a problem. On land, the hurricane can't suck up any more water, so it soon gets weaker and stops. But when hurricanes first blow over the land, they bring high winds and often floods that destroy houses and schools along the coastlines.
Global warming from using cars and heating houses with gas and oil makes the ocean water a little warmer every year, so there are more and more hurricanes, and more serious ones. That's going to keep getting worse.