What is longitudinal and transverse component of electric field? What is longitudinal and transverse component and how are they interpreted? 
 A: See for electromagnetic waves:
https://www.quora.com/Are-electromagnetic-waves-transverse-waves-or-longitudinal-waves
In a transverse wave the oscillation of the field is perpendicular to the direction of propagation of wave. In a longitudinal wave it is parallel to the direction of propagation of wave.
For the definition for waves in a material medium (non electromagnetic) and for intuition see:
https://www.physicsclassroom.com/class/waves/Lesson-1/Categories-of-Waves
"A transverse wave is a wave in which particles of the medium move in a direction perpendicular to the direction that the wave moves. Suppose that a slinky is stretched out in a horizontal direction across the classroom and that a pulse is introduced into the slinky on the left end by vibrating the first coil up and down. Energy will begin to be transported through the slinky from left to right. As the energy is transported from left to right, the individual coils of the medium will be displaced upwards and downwards. In this case, the particles of the medium move perpendicular to the direction that the pulse moves. This type of wave is a transverse wave. Transverse waves are always characterized by particle motion being perpendicular to wave motion."
"A longitudinal wave is a wave in which particles of the medium move in a direction parallel to the direction that the wave moves. Suppose that a slinky is stretched out in a horizontal direction across the classroom and that a pulse is introduced into the slinky on the left end by vibrating the first coil left and right. Energy will begin to be transported through the slinky from left to right. As the energy is transported from left to right, the individual coils of the medium will be displaced leftwards and rightwards. In this case, the particles of the medium move parallel to the direction that the pulse moves. This type of wave is a longitudinal wave. Longitudinal waves are always characterized by particle motion being parallel to wave motion."
