Can someone explain atan2 with a visual explanation?

Question

I'm trying to find the direction of a moving object and I came across the concept of using atan2 to do this (if the angle is > 180, then it moves in the opposite direction). I read the Wikipedia article which states : The function atan2 (y,x) is defined as the angle in the Euclidean plane, given in radians, between the positive x axis and the ray to the point (x, y) ≠ (0, 0).

I'm having difficulty understanding how the angle between two points would be calculated using atan2. Can someone explain this with a visual example?

Edit: I'm calculating the angle in Python using the following code which calculates the clockwise angle between two points:

import numpy as np

def angle_between(p1, p2):
    x = 0
    ang1 = np.arctan2(*p1[::-1])
    ang2 = np.arctan2(*p2[::-1])
    return np.rad2deg((ang1 - ang2) % (2 * np.pi))
```