Named 15yq100c and stored as a 74.9 KB PDF, the file is tagged as a schematic. The code follows the style of International Rectifier or Vishay Schottky rectifier part numbers, so a component datasheet is the likely content. It should give the package, pin arrangement, reverse voltage and current ratings needed to check a failed diode or select an equivalent in a supply's output section. Read the complete marking on the physical part and compare it with the document before trusting the ratings.
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.