Answer:
Tornadoes are divided into six categories of strength on the Enhanced Fujita Scale. In this scale damage is used to estimate a tornado's wind speed and that estimate is used to rate the tornado. Here are the categories with their corresponding wind estimates:
EF0: 65-85 mph (105-137 km/h)
EF1: 86-110 mph (138-177 km/h)
EF2: 111-135 mph (178-217 km/h)
EF3: 136-165 mph (218-266 km/h)
EF4: 166-200 mph (267-323 km/h)
EF5: over 200 mph (over 323 km/h)
The majority of tornadoes are rated EF0 or EF1, while the most damage and fatalities result from tornadoes rated EF3 and higher (the strongest 5% of tornadoes). On very rare occasions winds in a tornado can exceed 300 mph (480 km/h).
There are two main types of tornadoes: supercell tornadoes, which make up the majority of tornadoes and landspouts/waterspouts. Supercell tornadoes are generally the strong ones while landspouts and waterspouts don't usually exceed EF0 strength, though they have on occasion done EF3 damage.