A .rar file is a "Roshal Archive," a format used to bundle multiple files into a single, smaller package to save storage space and make it easier to transfer.
It uses lossless algorithms to shrink data size without losing information. FOR20-40.rar
Unlike many other formats, RAR files can include "recovery records" to help repair data if a file is damaged during transit. How to Prepare (Extract) the "Piece" FOR20-40.rar