Compressed RAR package covering the IBM ThinkPad A30 and A31 models, 3.25 MB in size. Its name states only the model pair, with no board number, revision or list of included files, so check what is inside after unpacking with WinRAR or 7-Zip. Archives of this kind usually hold schematics or service documents used to follow voltage rails, check signal paths and locate parts on the motherboard. Because A30 and A31 boards differ, make sure the document you use matches the system board installed in the machine on your bench.
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 @cyberlanelectonik. 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.