Do you mean easing for animations and such?
typically you just create a function with respect to t, time, and then you can constrain it. It’s usually between zero and 1, but spring animations tend to exceed one.
Bézier curves would be the most famous and widely used, since they can be computed quickly, and your control points allow for simple decision if the curves, and they’re différentiable so they can be guaranteed to behave smite me in the mathematical sense.