Interference is when two waves are coming towards each other and you want to determine what happens when the two waves meet. Interference occurs when waves in the same medium, meet at the same time, and at the same location. Superposition is when you add the two waves together to find out what happens to the amplitude at the point that they meet. A constructive interference is when the amplitude is higher (bigger) then the two initial waves. The destructive wave is when you add the two amplitudes the number should be smaller then the two initial waves. With a destructive wave there is a point where the two waves actually make a straight line. You still add the two amplitudes but the resulting number is smaller. With constructive and destructive waves after the waves have meet they continue on in the direction that they were initially going in. The last type of interference is a standing wave, that is when two waves are approaching in the same medium, same frequency, same amplitude, and traveling in opposite directions.