The file 16YQ045C is a 52.0 KB PDF filed under schematics, but the name describes a component code and gives no device, board number or revision. It follows the International Rectifier naming used for Schottky rectifiers, part of the same family as other 16YQ voltage grades. Expect a datasheet listing ratings, thermal figures and package outline. It is handy for sourcing an equivalent diode in a power stage; always confirm the stamped code and pin configuration on the original part before replacing it.
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.