What is the science definition of oscillation

Oscillation is the regular variation in magnitude or position around a central point.

Oscillation is a sway at regular speed going back and forth.

Synonyms:

Movevment, Swing, Wavering

 the model most likely represents the positions of earth, sun, and moon when there is: greatest difference between high and low tides
The high and low tides are created because of the combination of effects from the moon's gravitational forces with the sun's gravitational forces that affect the tide as the earth rotates