These are the Constructive Interference. When a crest/trough meets crest/trough from another source, their energies combine to result in  a greater displace, providing a bigger crest/trough.

This is the wave that has a destructive Interference. When the crest and the trough meet, they cancel each other out, and the wave becomes flat (it is hard to see that in my video).

This video shows the standing waves because the interfering waves have the same amplitude and wavelength. There are 4 nodes in the wave.