Small RAR containing a PDF named for a CPU socket, a generic name that gives no laptop model, board number or socket type. At 103 KB it is likely a single page or short excerpt, such as a socket pinout or a schematic section covering the processor connections. Technicians use such material to check power, ground and signal pins around the socket, find shorts and confirm voltage routing. Extract it with WinRAR or 7-Zip, then confirm the socket type matches your board before relying on pin assignments.
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 @generalschematics. 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.