Component datasheet in PDF for the 1N5400G diode, filed here under the schematic category even though it documents a single discrete part rather than a circuit. The G suffix is a manufacturer variant marking, often used for glass-passivated versions. At 220 KB it likely includes ratings tables, characteristic curves and package drawings. Technicians use it to confirm voltage and current limits, polarity and footprint before fitting a replacement in a power supply or input stage. Check the maker logo, since suffixes differ between vendors.
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.