Reference PDF, 171 KB, for the 2N5877 discrete semiconductor, labelled a schematic but most likely a manufacturer datasheet. The RE suffix in the name is not defined. JEDEC assigns 2N numbers to two-junction devices, the bulk of them bipolar transistors. The sheet is useful for identifying pins and reading voltage, current and power limits. It also shows the case outline, which matters when you need a replacement with matching mounting and thermal behaviour.
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.
Any PDF readerSumatraPDFFirefox / ChromeFlexBV (links PDF to boardview)