Just as Adobe strove to make its PDF file format the industry standard for sharing documents and forms, so now is the company aggressively trying to make PDF the standard for CAD and 3D file-sharing.
SKP is a 3D file format that is native to SketchUp software, a 3D modeling software. Like any 3D format, SKP files also store 3D models, and they consist of sketches, layers, model information, ...