A stationary wave is one that is not moving or is at a standstill or resting pose.
Whenever two waves with almost similar frequencies, wavelength, and amplitude traveling throughout opposing orientations collide, a standing wave is formed.
Conditions to have standing waves:
Whenever two traveling waves move in opposing directions and all have the same frequency response, they could generate a standing wave.
There will be times when the peaks of both oscillations will coincide. The subsequent wave will be formed by the addition of both peaks.
Whenever the apex of the first wave combines with the negative of such a second wave. The net amplitude would then be zero.
As a consequence, a standing wave forms. The waveform somehow doesn't move in the situation of a stationary wave.