Interpolation is the process of estimating the value of a function based on known values. In 3D animation it is the method used for calculating the in-between positions when animating a character moving between two poses. Blender also uses interpolation for generating geometry and other purposes. Use this tag for questions related to any of the uses of Interpolation in Blender.

Wikipedia says interpolation is

a type of estimation, a method of constructing (finding) new data points based on the range of a discrete set of known data points.

Blender uses interpolation to determine the in-between positions between two key frames in animation and has tools for doing so in 2D grease pencil animation. It also uses interpolation in tools that generate geometry from a known set of vertices.

Use this tag for questions related to any of the uses of Interpolation in Blender.