Archive of 1.76 MB named only after board LA-D991P, a number in Compal's LA-xxxxP format, which Compal uses on boards it builds for several laptop brands. The name does not say whether the package holds a schematic, a boardview or a BIOS dump, nor which laptop model or revision it fits, so open it and check the contents first. Confirm the LA code printed on your mainboard matches. If it holds firmware, back up the SPI flash before writing and check the image size against the chip.
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.