Archive titled TERESA20, 1.61 MB, where Teresa appears to be an internal project or board code name and 20 likely a revision, although the name does not spell out the device. Such code-named packages commonly hold schematics or boardview data used to trace power rails, follow signals and locate test points. Unpack it to see the actual files. Compare the code name and revision with the markings on the motherboard, since a different revision can have changed component placement and rail routing.
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.