The 2sk2790 name on this tiny 21.3 KB PDF is the only information provided. Filed as a schematic, it most probably holds a brief datasheet for an N-channel field-effect transistor, as the 2SK prefix denotes in Japanese JIS naming. Expect pin assignment and headline ratings rather than full characteristic curves. That is often enough to identify terminals and judge a replacement. Confirm the exact marking and package on the component before relying on it, and seek a complete datasheet for detailed specs.
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.