Transverse waves are the easiest to picture, because syou can visualize and often see material moving. Essential knowledge: Transverse, Longitudinal, Torsional and Love Waves.

Transverse waves

Longitudinal waves

 

sound waves:  http://onlinetonegenerator.com/

Torsional waves

Torsional wave demo – sticks, tape and jellie babies

Tacoma Narrows Bridge Collapse

Love waves