One point lighting is when light is only shining on one side of the person being photographed.

It creates a natural look. Often the side not lit shows a shadow

This is also reffered to as chiaroscuro. Chiaroscuro, is an Italian term that refers to the intense contrast of light (chiar) and dark (oscuro) in art, famously used in the paintings of Rembrandt or Caravaggio to create a strong and dramatic mood.