Cyclones cause huge damage every year, with loss of life and considerable damage to buildings as well. They normally happen around the Indian ocean, however can happen anywhere where the conditions are right. They are usually caused by several triggers, 1) warm or moist air, 2) wind blowing in different directions 3) Low wind, known as low wind shear 4) sufficient distance from the equator causing spinning.
They are low pressure systems over the tropics or sub tropics with organised convention. They are normally 5/6 miles high and 300/400m wide. They are normally about 10-15mph, however can be more. Anything above wind speeds of 74mph are considered to be hurricanes. Hurricanes are large cyclones.
Predicting cyclones is very difficult, often predictions from the sea are used, however, predicting them is considered a fine skill. Prediction is also done by people at specialist tropical cyclone forecasting centres around the globe such as the National Hurricane Center in Miami, Florida who are constantly studying satellite images, instruments and other weather data to detect and track them through their life-cycle.
Notable cyclones that you may have heard of Katrina - 2005 - Katrina was the most costly hurricane on record causing an estimated $75 billion in damage in Louisiana and Mississippi.