Original: Red Pikmin are the basic type, though more powerful than the other two varieties and resistant to fire. Yellow Pikmin can be thrown higher than the other two and can carry explosives called "bombs rocks", while blue Pikmin are the only ones that can survive in water.
Simplified: The Red Pikmin are stronger and can not be burnt, the Yellow Pikmin are lighter and can pick up bombs, and the Blue Pikmin can swim.