Transverse waves are the waves in which the medium particles vibrate to and fro about their mean positions at right angles to the direction of wave propagation. Transverse waves travel in the form of crests and troughs. One crest and the adjoining trough constitute one wave.
A simple example is given by the waves that can be created on a horizontal length of string by anchoring one end and moving the other end up and down. Another example is the waves that are created on the membrane of a drum. The waves propagate in directions that are parallel to the membrane plane, but the membrane itself gets displaced up and down, perpendicular to that plane. Light is another example of a transverse wave, where the oscillations are the electric and magnetic fields, which point at right angles to the ideal light rays that describe the direction of propagation.