Standing wave
Also called Stationary wave
A standing wave is the pattern produced when two identical waves travel in opposite directions through the same confined region. Instead of a moving waveform it has fixed points of zero displacement and fixed points of maximum oscillation.
AP Physics 2 EK 14.6.B.1: standing waves can result from interference between two waves that are confined to a region and traveling in opposite directions. In practice the second wave is usually the reflection of the first off the end of the string or pipe.
What makes it stand still. The two waves are permanently in step at some places and permanently opposed at others. EK 14.6.B.1.i: a node is a point on the standing wave where the amplitude is always zero, an antinode a point where the amplitude is always at maximum. The pattern oscillates in place; the crests do not march along the medium.
It transports no net energy. A traveling wave carries energy from place to place; a pure standing wave does not. Its two component waves carry equal energy in opposite directions, so the energy sloshes between kinetic and potential within each half wavelength and travels nowhere along the string.
Only certain wavelengths fit. EK 14.6.B.1.ii says the possible wavelengths are determined by the size and boundary conditions of the region to which the wave is confined, and EK 14.6.B.1.iii names the common cases: pipes with open or closed ends, strings with fixed or loose ends. The longest wavelength that fits gives the fundamental frequency.
A standing wave is superposition applied to a wave and its own reflection, nothing more.