PLY was designed at Stanford's 3D scanning lab by Greg Turk (1994) to store scanned geometry, and it remains the standard output of 3D scanners and photogrammetry pipelines (Meshroom, RealityCapture, COLMAP). A fully self-describing header declares elements and typed properties, so files can carry per-vertex normals, colors, and confidence values alongside positions. Three encodings exist and all are common: ascii, binary little-endian, and binary big-endian. Blender imports and exports PLY natively.
How to open
Blender (File > Import > Stanford PLY), MeshLab, and CloudCompare all open PLY, including point-cloud-only files. Windows 3D Viewer reads mesh PLYs. The ascii flavor is inspectable in any text editor.