What it is?
Angular momentum is momentum of an object moving in circles, which includes radius.
Let's make it more visualisable.
imagine a point somewhere in space, let's say an aobject is moving around the point in space (The objects revolution arount the point).
if we calculate the mass, velocity of the object moving around the point, and the radius(distance from the point and the object) you get the angular momentum.
Watch this video, for better visual understanding. ==>
An example