The 2SK2312 is covered by this 391 KB PDF, catalogued under schematics yet most likely a component datasheet. Japanese JIS numbering assigns the 2SK prefix to N-channel field-effect transistors. Typical contents are absolute maximum ratings, electrical characteristics, safe operating area and package drawing. Technicians consult it before replacing a failed MOSFET in a supply or motor-drive stage, making sure the substitute meets voltage, current and on-resistance needs. Check the physical part marking and package against the document first.
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.