How many types of seismic waves are there?
There are three type of seismic wave.
Primary (P) waves are longitudinal, the fastest, the least destructive (lowest amplitude) and they can travel through water, air and solids.
Secondary (S) waves are transverse, medium speed (relative to the others), second most destructive and can only travel through solids.
Surface waves have two different types (love and Rayleigh), can be longitudinal or transverse, are the slowest but most destructive and travel along the surface of a planet between two mediums (substances)
Hope this helps; let me know if I can do anything else:)
(I also wrote a longer answer around this that can be found here )