The 2SB621 in this 51.4 KB PDF is a PNP bipolar transistor according to the JIS prefix, so the file, filed under schematics, should be a part datasheet; _E most likely marks the English edition. Expected content includes absolute maximum ratings, electrical characteristics, hFE classification and a package drawing showing which pin is which. Repairers use these specifications to test the device with correct PNP polarity and to qualify cross-reference replacements before fitting them in place of a failed original.
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.