What is a synapse and how does information pass across it?

A synapse is a junction between two neurones.

Information is passed from one neurone to the other in the form of a chemical (which is also known as a neurotransmitter). The chemical (neurotransmitter) is released from the first neurone, diffuses across the gap, and stimulates the second neurone. The first neurone is known as the presynaptic neurone, and the second neurone is called the post synaptic neurone. The 'gap' it passes through is called the synaptic cleft.

I would use a diagram to help show this.