Floods and mudslides are both occurrences, which can be very destructive.
(Hopefully after the edit the question is more clear)
What is the difference between a flood and a mudslide?
A flood occurs when land that is normally dry is covered by water. The source of the flood water is generally from bodies of water, such as: rivers, lakes, dams and even the ocean.
Rivers can flood, when:
the flow rate exceeds the capacity of the river channel
Similarly, excess water run-off during heavy rain can cause floods when the water cannot drain away quickly enough.
Flooding is the act of flood water accumulating in a area that is being flooded.
To understand mudslides you need to know what a landslide is.
A landslide is when a quantity of rock slides down a slope.
A mudslide is similar to a landslide. The only difference being the type of material that is moving. With landslides, the material moving is generally composed of rock and maybe some soil. In mudslides, the material being moved is loose, finer grained material such as mud and clay.