Datasheet-style PDF, 217 KB, for the 2SC3668 transistor; the name supplies no other details. Parts numbered with a 2SC prefix under the JIS system are NPN bipolar transistors. Though catalogued as a schematic, the content is likely specifications such as Vceo, Ic, power dissipation and hFE, plus the package drawing. Use it to check pin assignment before desoldering or testing with a multimeter in diode mode, and confirm that any replacement shares the same footprint and lead order.
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.