The 182 KB PDF bears the name 2SC5712, a JIS designation pointing to an NPN bipolar transistor, so it is presumably a datasheet despite the schematic label. Further details are not stated. Inside you would normally find the package drawing, absolute maximum ratings and characteristic tables. These help when measuring a suspect part on the bench or matching a replacement by voltage, current and gain. Compare the case style with the board footprint to avoid pin order mistakes.
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.