The Superior Colliculus is a structure within the brain that receives visual information from the optic tract and then sends that information to parts of the parietal lobe and the temporal lobe. This structure is responsible for our attention to visual and auditory stimuli and helps us to coordinate our eye movements and reflex actions.
The Superior Colliculus plays a role in consciousness by filtering out some stimuli in the environment and paying attention to other stimuli. A good example of this is known as "the cocktail party effect." When you are in a crowded room with lots of conversation, the Superior Colliculus is able to "filter out" the conversations that aren't important and allows you to shift from one conversation to the other.
The Superior Colliculus also sends output to motor centers that are responsible for reflex actions. If something potentially dangerous is present, your Superior Colliculus sends messages to the brain stem to activate a response reflex that will help you avoid potential danger.
Some information in the above entry was found (but not cut and pasted) from Biological Psychology, by Stephen B. Klien.