Around 173 KB of PDF datasheet material for the 2SC5307, an NPN bipolar transistor in the Japanese JIS 2SC series. The name gives no maker, package or intended circuit. Categorised as a schematic, the file should present maximum ratings, characteristic data and mechanical dimensions. It serves for identifying pins, judging whether a component has failed and sourcing an equivalent with adequate voltage and current capability. Related variants such as 2SC5305 are different parts, so match the marking on the component carefully.
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.