Answer: in doing transformations, the pre-image is the image you start with. The task is to move the pre-image so that it is contiguous with the (target) image. This is typically done by translation, rotation or reflection or a combination of those moves.
Image is a related term of preimage. Preimage is a derived term of image.
In context terms the difference between preimage and image is that preimage is the set containing exactly every member of the domain of a function such that the member is mapped by the function onto an element of a given subset of the codomain of the function formally, of a subset b'' of the codomain ''y'' under a function ƒ, the subset of the domain ''x defined by while image is the subset of a codomain comprising those elements that are images of something.
As nouns the difference between preimage and image is that preimage is the set containing exactly every member of the domain of a function such that the member is mapped by the function onto an element of a given subset of the codomain of the function formally, of a subset b'' of the codomain ''y'' under a function ƒ, the subset of the domain ''x defined by while image is an optical or other representation of a real object; a graphic; a picture.