The 2SK2915 is covered by this 434 KB PDF, indexed under schematics but most likely a component datasheet, since the name carries only the transistor number. Japanese 2SK designations refer to N-channel FETs, frequently found in switching power supplies, inverters and load switches. The document is useful for checking absolute maximum ratings, on-resistance, capacitance and the package drawing when replacing a failed device. Any PDF reader opens it; compare the body marking and package with the drawing before fitting a part.
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.