A reflex is a quick, involuntary response to a stimulus.
These are automatic actions that do not require thought, but are situation specific. Examples of reflexes are pulling your hand away from a hot object, or blinking when something lands in your eye. These are in contrast to voluntary actions, such as raising your hand in class, or involuntary actions that occur regularly, such as breathing or the muscle contractions of digestion.
Many reflexes help you not get hurt or die; they are an aspect of self-preservation. Evolutionists attribute the existence of such reflexes to the principal of "survival of the fittest"--those that responded quicker to these dangers were more likely to survive and these response times were passed on. In contrast, intelligent design might purport that these reflexes were gifts from God and part of His protection for us.
The difference between evolutionists and Intelligent Design becomes more apparent when one considers another class of reflexes. These are the emotional, or empathetic, reflexes because they involve empathy for other people. For example, if you see an old lady trip, you reflexively reach out to catch her. If you see someone get hurt, you reflexively wince in shared pain. God has given us these reflexes to encourage us to help our fellow man when he is in need. The existence of these reflexes reveals the limited scope of "survival of the fittest," which would only imply that you would help your immediate progeny, out of a selfish interest in continuing your genetic legacy. It is also worth noting that animals do not possess these empathetic reflexes (even though they possess self-preservation reflexes). The animal may react with fear at a fellow animal's yelps of pain, but if it sees a fellow animal in danger, rarely does it help the other animal (unless it is progeny). This difference between man and animal is further evidence of the special role of humans in God's Design.