A typical machine will have a number of built-in sessions that provide sequences of changing stimulation, designed by the session composer using the basic repertoire of machine features. Some machines are programmable, meaning the user can create his or her own sessions, and some can download sessions from a personal computer. The quality of the built-in sessions is very important unless you plan to compose everything yourself. Different people have different reactions to sessions, so using one of these machines is a bit of an exploratory journey. You can move your eyes and change the effect, you can concentrate on the patterns and change what they seem to be doing.
Some people report seeing visions in the patterns as the imagination is inspired to work.
The stimulation takes over your two main sensory inputs, and not surprisingly has an effect on your mental state. Music has been doing this for centuries, without the assist from coordinated flickering lights. Intermittent use is not effective until you have learned how to respond to the stimulation. They can be used safely by untrained persons for relaxation, learning enhancement, meditation tools, and many other purposes, but not for relief from any medical condition. If you are seeking help for a medical condition, please see a trained professional.