Only the part code 2N5657 identifies this 497 KB PDF, which the index lists under schematics. The 2N prefix belongs to the JEDEC registration system for discrete semiconductors, so a datasheet is the most likely content instead of a circuit diagram of a board. It is useful when identifying leads, reading breakdown and power ratings, or choosing a replacement in a power or linear stage. No manufacturer, board or device is named, so confirm the component marking and package before trusting the values.
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.