A 111 KB PDF for the 2SD2281, which under the Japanese JIS system is an NPN transistor from the low-frequency 2SD series. The file is tagged as a schematic but most likely holds the manufacturer datasheet, giving electrical characteristics and the mechanical outline. It is useful when diagnosing a shorted transistor or substituting an equivalent, because it shows pinout, voltage and current limits and dissipation. The name offers only the part number. Verify the package and printed marking on the board before trusting the specifications.
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.