The bare part number 2SC3419 names this 176 KB PDF, which the index lists as a schematic. Under JIS conventions the 2SC prefix identifies an NPN bipolar transistor, so the document is likely a datasheet. A repair technician would use it to check base, collector and emitter positions, maximum ratings and the mechanical outline when replacing the device or evaluating an equivalent. Compare the printed code, commonly C3419, and any suffix on the original part 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.