15mq040n is the name on this 94.2 KB PDF, which the catalogue files as a schematic. The code resembles International Rectifier or Vishay surface-mount Schottky rectifier numbering, so expect a datasheet covering reverse voltage, forward current, leakage and footprint dimensions. Such data helps when tracking down a shorted protection or rectifier diode on a compact board and choosing a footprint-compatible replacement. The trailing letter may denote a variant, so check the full marking on the part.
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.