RAR package for the ECS D1F-AD motherboard, revision 1.0, about 826 KB in size. The name gives only the model and revision, with no chipset or platform details. Repair data like this is typically used to trace power rails, locate components and test points and narrow down shorts or missing voltages on a dead board. Unpack the archive to see whether it contains a schematic, boardview or firmware, as the name does not say. Match the D1F-AD model and Rev 1.0 printed on the PCB before relying on it.
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.