Service schematic for the Bose AM15P, as named in the file, likely an amplifier or powered bass module from an Acoustimass-type speaker system. The 618 KB PDF should cover the amplifier, power supply and input sections. Technicians use it to trace supply rails, check output devices, follow the signal path and locate protection circuitry when a unit hums, distorts or stays silent. Compare the board markings and revision on your unit with the drawing before changing parts, as Bose revised these assemblies over production.
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 @pdf_servicemanual. 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.