Schematic in PDF format, archived as C21_vc, with no brand, model or board number given. C21 is likely a project or board code, but the target device cannot be confirmed from the name, so open it and read the title block to identify it. Once matched to the board, a schematic like this is used to trace power rails, follow signal lines, locate components and work through no-power or short-circuit faults. Check the revision against the PCB before trusting values.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @schematicslaptop. Enginerys does not host this file.
How to open a .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.
7-ZipWinRARThe Unarchiver (macOS)