Datasheet in PDF form for a component identified as SM5K6, a 281 KB document. The name gives only the part designation, with no manufacturer or revision stated. A technician typically opens a datasheet like this to confirm pinout, package marking, absolute maximum ratings and typical application circuit before replacing a suspect part on a board. Compare the marking on the physical component with the part number inside the PDF, since similar-looking codes from different makers can describe unrelated devices.
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 @datasheet_technar_org. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.