Bearing only the JIS part number 2SC2879, this 167 KB PDF is listed as a schematic. A 2SC designation marks an NPN bipolar transistor, so the file most likely contains the part datasheet with ratings and package data. The name offers no maker, package or revision details. Technicians use such sheets to verify pinout and maximum ratings, judge whether an equivalent is adequate and read characteristic curves. Before relying on it, make sure the code printed on the original component really matches this number and package.
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.