The first video is an example of standing waves, we can see that in the wave there are points that appear not to move which are called nodes.
The second video is an example of contructive interference between waves which is when a crest is combined with a crest or a trough is combined with a trough and their algebraic value adds together to form a bigger wave at that point in time when they intersect.
The third video is an example of destructive interference betweeen waves which is when a crest and a trough are combined and they cancel out at the point in time when they intersect.
Noise cancelling headphones use destructive interference. They analyze the surrounding sound and they produce waves that cancel out the waves that come in and therefore cancel out the sound of background noises.