Specification PDF of 34.9 KB for the 2sk2577, grouped under schematics although the name is a plain part number. The JIS 2SK prefix identifies an N-channel field-effect transistor, so this is presumably a brief datasheet. Its practical use is confirming which leg is gate, drain and source, and reading voltage, current and power limits when diagnosing a failed stage or choosing a substitute. Always check that the component marking and package match before ordering or fitting a replacement.
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.