PDF document for the IRFP260 power MOSFET, catalogued under schematics although the name points to a component datasheet. At 174 KB it most likely holds the manufacturer's ratings, characteristic curves, TO-247 package outline and pin assignment. Technicians use such a sheet to confirm gate, drain and source pins, compare voltage and current limits when choosing a substitute, and interpret readings taken with a diode tester. Check the exact part suffix and manufacturer on the device body before relying on the figures, since variants differ.
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.