The 2SB906 transistor is the subject of this 196 KB PDF. Following JIS designation, 2SB parts are PNP bipolar transistors classed for low-frequency use. Nothing else is encoded in the name. Listed as a schematic, the file is most likely the component data sheet, holding absolute maximum ratings, gain grades, saturation figures and the mechanical outline. Check those values and the lead order before substituting a part, and inspect adjacent components, because a shorted transistor often damages its driver or base resistors.
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.