Part-number PDF for the 2SC4107, 93.2 KB, stored in the schematic category. Nothing in the name points to a specific device or board; the 2SC prefix marks an NPN bipolar transistor in the Japanese semiconductor naming scheme, so this is almost certainly a component datasheet. Technicians consult such pages for ratings, hFE grouping, SMD marking and pin layout when testing a transistor with a multimeter diode mode or selecting a substitute. Confirm the package outline before replacing the original 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.