Indexed as a schematic, this 105 KB PDF actually carries a semiconductor part number, 2SC4406. In JIS designations 2SC identifies an NPN bipolar transistor, so expect a datasheet describing characteristics, limits and package. Technicians use it to read the pin arrangement, check whether a substitute can handle the same collector voltage and current, and match the footprint. The file name contains no other information; verify the marking and case style of the part on the PCB before relying on it.
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.