Skeching is really simple its all about finding the refrence item/image and break it down to simpler shapes
Then you modify the simple shapes to make the actual shape of the subject and then you erease the simple shapes.
And finnally you add detail and shading
Point perspective
Perspective drawing is a style of sketching that helps to sketch
In more than one point perpective you can see diffrent angles like for example buildings in 2 point perspective are drawings were you can see two sides of an object, Most commonly a building