RAR archive, about 1.42 MB, labelled Dell 510, probably the Latitude or Inspiron 510m notebook line, though the name does not say which. No board number or revision is given, so treat the contents, likely a schematic or related service drawing, as unverified until opened. Such files help follow power rails, signal paths and component references when repairing a board. Always check that the PCB number and revision on your unit match the document title block, since ODM boards for one model may vary.
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.