Every part of the brain does some specific functions. For example, frontal part of the brain is our think centre, spinal cord and medulla oblongata regulates our heart rate and breathing pattern.
A synapse is the junction between the two neurons. Consider this as a joint in an electric wire junction. In an electrical wire, electricity passes two wire through the joint by electron transfer.
You must have observed that when our hand comes in contact with fire, it spontaneously retracts away from the fire. When someone blows air to our eyes, we close the eyes.In all these happenings, our body responds to stimuli unknowingly,