Click the green arrow to see examples of different tweening methods. The bananas finish at roughly the same time but they move in quite different ways. Tweening is a term used in animation, derived from the phrase "in betweening". When drawing an animation of a moving object an animator might start by drawing the start position, drawing the end position, then drawing the frames in between.
Objects in the real world rarely move in a linear fashion, they move at different speeds from moment. By using different tweening techniques you can bring life to your animations!