The Realtek RTL8191SU Selective Suspend Enabler is a driver or utility that enables power management features for devices using the Realtek RTL8191SU Wi-Fi chipset. This chipset is commonly found in wireless USB adapters that provide connectivity for computers or other devices. The "Selective Suspend" feature helps save power by allowing the device to enter a low-power state when it's not actively in use, without disconnecting or losing the connection.

In Windows, Selective Suspend is a feature that allows USB devices to enter a low-power state when they are idle. The Selective Suspend Enabler specifically ensures that this feature is supported and works correctly for devices that use the Realtek RTL8191SU chipset.