Tornadoes form due to large pressure differences in regions. It is like a whirling (circling) air with low pressure inside and high pressure outside. The air whirls at high speeds and has power to lift houses, vehicles etc. into air. It is usually formed on land and travels at high speeds along the land, destroying everything on its way.
A hurricane is similar with pressure differences inside and outside. It is formed over water bodies. These hit the coast of the water body with a lot of devastating effect. They destroy property and coast. They are usually associated with strong winds along the coast, and rain.