Covering the 2SK1828, this 319 KB PDF is catalogued as a schematic but is most likely the component datasheet. The 2SK prefix in the Japanese JIS system designates an N-channel field-effect transistor. Expect maximum ratings, electrical characteristics, graphs and a package outline. A repair technician reads it to identify terminals, understand the voltage and current headroom and find a suitable substitute for a shorted device. Confirm the footprint and ratings match before soldering in any replacement 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.