Only 28.2 KB, this PDF named 2sk123 is catalogued as a schematic, but the name is a JIS transistor number, so a short datasheet is the likely content. Parts carrying the 2SK prefix are N-channel field-effect transistors. A repairer uses it to confirm which leg is gate, drain and source and to check voltage and current limits before installing a replacement. Expect a condensed specification; confirm package style against the board, and protect the new FET from static discharge during fitting.
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.