A 30.5 KB PDF for the 2SK2631, filed among schematics though the number is a JIS N-channel FET designation, meaning the content is a component datasheet. Expect a concise summary of maximum ratings, electrical characteristics and the package with its pin order. On the bench it helps when checking a transistor out of circuit or matching a substitute to the original's voltage and current capability. Confirm the exact marking first, since adjacent part numbers are different 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 @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.