Enumeration is the process by which a bus driver discovers the devices attached to it, reads their identifying information and reports each one to Windows so that Plug and Play can select drivers.
In practice
When a laptop wakes from sleep, the USB bus enumerates again, finding each connected device, reading its descriptors and reporting identifiers. That is why a dock's devices can briefly disappear and return in Device Manager after waking.
Common confusion
Enumeration is not driver installation; it only finds and identifies devices. A device can enumerate successfully and still lack a driver, appearing under Other devices. Nor is it continuous scanning: it happens on connection, startup and certain state changes.
Why it matters to readers
Understanding enumeration explains event entries, faded remembered devices and why moving a device to another port creates a new instance.
A closer look
Different buses enumerate in different ways. PCI Express enumeration happens mainly at startup, when firmware and Windows walk the bus and record each component. USB enumeration happens whenever something is connected, and each hub reports changes on its own ports. Bluetooth discovery is related but involves pairing, which adds user confirmation before a device is set up. Each approach ends the same way, with identifiers handed to Plug and Play.
