Part number 2SK2231 is the only information carried by this 420 KB PDF, which the index places among schematics but which most likely documents a single transistor. JIS/EIAJ numbering assigns 2SK to N-channel field-effect devices; the maker and case style are not given. For bench work the useful content is the pinout diagram, absolute maximum ratings and characteristic curves. Together these let you select a correct substitute and avoid fitting a part with a lower voltage or current rating.
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.