What is the spherical coordinate system? 

What is the spherical coordinate system? An oscillating charge produces the radiations of spherical pattern.

In spherical coordinates a point P is represented by three components that are (r,Θ, Ф). R is the radius of the constant spherical surface, Θ is the angle of the radial line that it makes with z-axis, Ф is the angle of projection of radial line with x-axis.

The follow lecture describes the complete detail of spherical coordinate systems.

Relation between spherical and cartesian coordinates systems

https://www.youtube.com/watch?v=zcoOkG7ppV0

Also read here

https://eevibes.com/electromagnetic-field-theory/what-is-the-cylindrical-coordinate-system/

what is the cylindrical coordinate system?