Quick start

1. Open Ease.blend (File > Append > Node Groups > Ease). Add a Geometry Nodes modifier and put Ease in it, or add it in the node editor with Shift+A > Group.
2. Connect any 0 to 1 value to Value (Value node, frame / frame count, Index / Count, a driver).
3. Pick Type and Direction. Read the eased number from Result.

Settings

Simple: Midpoint, Strength, Overshoot, Bounces, Bounciness, Steps. Advanced: Elastic Shape (Amplitude, Period), Start Shift (Elastic Start, Bounce Start), Looping (Loop, Cycles), Output Range (Min, Max, Clamp).

Other files

Ease Graph draws the curve in the viewport. Ease Shader is the shader version. Ease Examples.blend has 27 working examples: press Space to play. The PDF manual explains every setting.