ESS Maestro PCI Audio (WDM) Windows Driver refers to the software driver that enables your Windows operating system to communicate with an ESS Maestro series sound card, which is a PCI-based audio interface used for processing sound and audio output. The "WDM" in the name stands for Windows Driver Model, which is a standardized driver framework used by Windows operating systems to provide support for various hardware devices like sound cards, printers, and more.

When you install this driver, it ensures that your ESS Maestro PCI sound card functions properly on a computer running a Windows OS. The driver is responsible for managing audio input and output, as well as supporting various audio formats, 3D sound, and mixing functionalities.