A tornado is formed when huge masses of clouds moving in different directions meet. The air starts to spin in a spiral and a funnel of twisting air reaching out towards the ground. The low pressure inside the funnel sucks up the soil, dust and anything else it touches.
Tornados are violent destructive whirlwind whose force is concentrated into a much smaller area than a hurricane. They travel across land at very high speeds and the roaring noise the make can be heard 40km away.