The 2SC3938 sheet arrives as a 46.3 KB PDF with an _E suffix, which on Japanese component documents typically signals an English edition. Though indexed as a schematic, it should be a datasheet for this JIS-numbered NPN bipolar transistor. Expect absolute maximum ratings, electrical characteristics and an outline drawing for pin identification. Use it when measuring junctions or evaluating an equivalent, and confirm the shortened C3938 marking and case on the board match first.
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.