Most light sources can be considered one of the following:
A directional light source emits parallel light beams, and doesn't fade over distance, unlike other types of light sources. Directional light mimics day light, light emitted from a very strong and very distant source.
Point lights are omni-directional. Light beams are emitted from a single point in space and spread out in all directions. Each beam of light gets further from each other over distance, and therefore the light gets weaker the further from the source. Examples of point lights are bulbs and candles.
Spot lights emit a cone of light behaving in a similar way to a point light, only in a cone shape. Light is emitted from a single source and radiates out at a less than 180° angle. Examples of spot lights are stage lights and street lamps.
In general, ambient light is bounced light, and therefore not emitted by a source, but for the sake of understanding let's consider ambient light a global light source, light coming from all directions, without casting shadows. We can think of ambient light as a general level of lighting in a scene.
Shadows come in two types:
A form shadow is the dark side of an object, the areas facing away from the light source.
A cast shadow is the dark area that appears when an object obstructs a light source, preventing the light beams from contacting another object or surface. The result is a shape of the object between the light source and surface.
We'll go a bit further with light and shadow in future tutorials.