Indexed as a schematic, the 305 KB PDF named 2SK208 most likely holds the datasheet for that Japanese JIS-numbered part. The 2SK prefix designates an N-channel field-effect transistor. Opened in any PDF reader, it supplies gate, drain and source pin positions, package details and electrical limits needed when replacing or substituting the device. FETs can be damaged by static, so handle replacements with care, and confirm the exact marking and any grade suffix on the original before ordering a part.
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.