A 410 KB PDF describing the 2SK2542, a JIS-numbered part where 2SK signifies an N-channel FET. Beyond the part number the name gives nothing, so maker, case style and revision must be checked inside the file. For a bench technician the useful content is the pin assignment, breakdown voltage, drain current and on-resistance, which matter when testing a suspect device out of circuit or choosing an equivalent. Match the component marking against this number before trusting the data.
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.