PDF covering the 2SC3621 transistor, 207 KB in size. JIS designation assigns the 2SC prefix to NPN bipolar transistors; the file name gives no other device details. Despite the schematic category, this is most likely a datasheet with ratings tables, electrical characteristics and the case outline. Repair technicians rely on such a sheet to read the correct pinout, check limits against circuit voltages and choose a suitable equivalent with the same package when the original part is unavailable.
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.