The 2SK1736 is documented in this 92.6 KB PDF. Under JIS designations, 2SK means an N-channel FET, so the file is almost certainly a component datasheet despite its schematic label. It should present absolute maximum ratings, characteristic data and a package drawing. Technicians use it to read the pinout, check voltage and current limits and compare candidate replacements after a failure. Since the name gives only the part number, confirm package and marking on the actual board 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 @cyberlanelectonik. 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.