For the 2SJ579, this 42.7 KB PDF is indexed as a schematic, but a bare part-number name typically marks a datasheet. The 2SJ code follows the Japanese JIS convention for P-channel FETs. Expect electrical characteristics, absolute maximum ratings and a package outline, which help when checking a suspect transistor or choosing a substitute with equal or better ratings. Since nothing else appears in the name, compare the body marking and footprint on the board before relying on the figures.
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.