Named 2SC2458, this 340 KB PDF relates to an NPN transistor registered under the JIS system, where 2SC marks NPN types. Although the index calls it a schematic, it is most likely the manufacturer's datasheet. Technicians use it to confirm limiting values, gain classes and pin assignment when replacing a failed small transistor. A separate L-suffixed version of the part also exists in this collection, so match the exact suffix on the original component before ordering.
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.