The 2SK2605 is the subject of this 411 KB PDF, filed as a schematic although its name is purely a semiconductor part number. In JIS nomenclature the 2SK prefix stands for an N-channel FET, so the content is most likely the manufacturer datasheet. Such sheets give pin layout, package dimensions, breakdown voltage, drain current and gate threshold figures, useful when measuring a suspect transistor with a meter or finding a modern equivalent. Make sure the component marking agrees 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.