ECS P23G board files in a 829 KB RAR archive; the name gives neither a revision nor a description of the contents. Read the revision from the PCB and compare it with the title block of any schematic inside. Typical material of this size is a circuit diagram or a firmware image, used to trace power rails and signals, find the source of a short, or reprogram a corrupted BIOS chip. Extract and check the files first, and back up the existing chip before writing anything.
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 @IT_SERVICE_WORLD. 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.