The Lexmark MX420 Series PostScript 3 Emulation Windows driver is a software package that allows your Lexmark MX420 Series printer to communicate with a computer running a Windows operating system, particularly for printing tasks. The PostScript 3 Emulation refers to the printer's ability to emulate PostScript 3, which is a page description language (PDL) used for high-quality printing. PostScript is commonly used in professional printing and graphics applications because it allows for precise control over text and graphics.

The PostScript 3 Emulation means that while the printer might not have a native PostScript interpreter built-in, it can simulate the behavior of PostScript 3 to support a wide variety of high-quality print jobs, particularly those that involve complex graphics or fonts. This is especially useful for users who require PostScript-compatible applications or workflows.