Spherical coordinate system

In mathematics, a spherical coordinate system specifies a given point in three-dimensional space by using a distance and two angles as its three coordinates. These are the radial distance, r, along the line connecting the point to a fixed point called the origin; the polar angle, θ, between this radial line and a given polar axis; and the azimuthal angle, φ, which is the angle of rotation of the radial line around the polar axis.

Source: Wikipedia — Spherical coordinate system (CC BY-SA 4.0)