The 2SK3291 transistor is the subject of this 34.2 KB PDF, filed as a schematic although it works as a datasheet. Under JEITA designation rules, 2SK parts are N-channel field-effect transistors. Technicians open such files in a PDF reader to confirm the pinout before in-circuit testing, to read absolute maximum ratings, and to find a suitable replacement with matching package and characteristics. Only the part number appears in the name, so maker and ratings come from the document.
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.