A vendor-neutral file format for storing point cloud data captured by laser scanners, designed so scans from different hardware can be shared and processed the same way. Before E57, every scanner manufacturer had its own proprietary point cloud format, making it hard to move a scan between different reality capture and BIM tools. It's now the closest thing the scan-to-BIM workflow has to a common exchange standard, alongside LAS for airborne and mobile LiDAR data.