An SKP file is a three-dimensional model created by SketchUp, a 3D design program. It contains a model with wireframes, shades, edge effects, and textures.
The SKP file enables conceptual designs to be created, viewed, and shared quickly and easily. When you create a new document and save it in SketchUp the SKP file is created to store the document and its contents. SKP files can also be used to store SketchUp components. Components may be made by you or another user and can be imported into an SKP document to be inserted into your model.
AutoCAD DXF (Drawing Interchange Format, or Drawing Exchange formal) is a CAD file format created by Autodesk for AutoCAD more compatible with other programs.
DXF was initially intended to represent exact copy of the data in the AutoCAD native format DWG (Drawing).
It can’t hurt if we mention that DXF coordinates come always without dimensions so the user needs to know the drawing unit or has to extract it from the textual comments in the sheets.