Interference is a phenomenon that occurs when two or more waves combine to form a new wave pattern. This can happen in a variety of contexts, such as when light waves interact with each other or when sound waves interact with each other. Interference can be either constructive or destructive, depending on the phase relationship between the waves.
Constructive interference occurs when the waves are in phase, meaning that their crests and troughs line up. This results in a new wave that has a larger amplitude than either of the original waves. Destructive interference occurs when the waves are out of phase, meaning that their crests and troughs do not line up. This results in a new wave that has a smaller amplitude than either of the original waves.