Datasheet-style PDF for the 2SK1412LS, a Japanese 2SK-series N-channel field-effect transistor, filed in the index under schematics. The LS suffix usually marks a package or lead variant of the base 2SK1412, so compare the marking and outline against the part on your board. At 30.3 KB it is likely a short sheet with ratings and pinout. Technicians use such a sheet to confirm gate, drain and source pins, check voltage and current limits, and pick a valid substitute before replacing a shorted MOSFET.
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.