One of the basic stage lighting tools is a filter. Whether it's the side of a glass bottle or a specially made lens, light is shone through a filter to achieve a certain effect on stage. Whether the effect is to turn the light red, make it appear watery, or produce flickering shadows, a filter can be set up to create the desired effect. You can purchase filters in a variety of sizes and types, but the lighting team can also improvise a set for your production.
A spotlight is a tool that's used to draw attention to a particular part of the stage, usually where a performer will stand. The spotlight is mounted on the catwalk and shone down onto the stage, just like many of the other lights. The advantage of a spotlight is that it can be swiveled to follow an actor as he moves across the stage. This helps focus the audience's attention, and in some productions it may distract attention from stage hands who must make subtle changes to the scenery while the scene is still going on.
While it is possible to have several stage hands and tech people each controlling individual lights or parts of the lighting system, an automatic light controller is a very handy tool to have. All the stage lights are wired into this device so they can be controlled from a single location (usually the sound/lighting booth at the back of the theater). Automatic light controllers allow a single person to control a large portion of the lights, which cuts down on the amount of work delegated to other lighting techs.