802.11u is a 2011 amendment to the 802.11 standard that enables seamless Wi-Fi roaming and network discovery (Independent of the SSID of a WiFi network).
Although often used interchangeably with Hotspot 2.0 and Passpoint, these terms have distinct meanings.
While they share common goals and technologies, Hotspot 2.0 typically refers to the Wi-Fi Alliance's certification program, Passpoint is a specific implementation, and 802.11u is the underlying standard.
In practice, however, these terms are often used loosely to refer to the same general concept of advanced Wi-Fi roaming and network selection.
In short, it allows your device to connect to a WiFi network without being dependent on the SSID that is broadcast on the specific WiFi network.
802.11u enables devices to connect to Wi-Fi networks based on other identifiers, such as:
Domain names
Roaming consortiums
Network identifiers
So the key takeaway,
802.11u,
Hotspot 2.0 and
Passpoint are all part of the same WhatsApp group

Next we will look how this is accomplish on the WiFi Access Point.