The simplest form of light is called hard light. This is the kind of light that is created when a light source has no covering on it, like a bare light bulb. The shadows that it casts are hard, meaning the edges are sharp and clearly defined. This produces a dramatic, intense look that may be appropriate for some scenes, but it should never be used as a default simply because a cinematographer or photographer lacks the skill to produce other lighting effects.
For a softer touch, the image maker can employ diffused light. Unlike hard light, this soft, gentle light produces shadows with soft edges, giving a softer, more pleasing tone to the image. This is the most popular light today in photography and cinematography, and it is created by placing a diffusion material, like a lamp shade, soft-box or photographic umbrella, between the light source and the scene in order to scatter the light rays and create softer edges on the resulting shadows.
Mixed light is the type of light we most often encounter in our daily lives. It occurs when light from a soft source and a hard source mix together, creating two different styles of shadows. This effect can be employed creatively, as well, though mixing the two types of light can be challenging for a beginner. Experiment with placement and combination until you find a look that you like, and don't forget that much of what you learn about light will come from experience.
While the style of light has a powerful effect on the resulting image, different lighting effects can also be employed. This include flags and GOBOs, which block the light from falling on a particular part of the scene; colored gels, which are plastic sheets applied over the light to give it a specific color; grids, which focus and soften the light simultaneously; and a host of other special accessories designed to help your lighting look more natural, dramatic and effective.