An SSID (Service Set Identifier) is a unique name that identifies a wireless local area network (WLAN). When a user sets up a Wi-Fi network, they choose an SSID which is then broadcast to nearby devices to allow them to connect to the network. The SSID acts as a sort of "username" that devices use to connect to the network.

Each Wi-Fi network is associated with a unique SSID, and a single device can be connected to multiple Wi-Fi networks by switching between SSIDs. When a device is within range of multiple Wi-Fi networks, it can see the available SSIDs and connect to the one with which it is configured.

SSIDs are typically used to distinguish between different Wi-Fi networks, making it easy for users to select the correct network when connecting their devices. They can also be used for security purposes, as a Wi-Fi network with a hidden SSID will not be broadcast to nearby devices, making it more difficult for unauthorized users to connect to the network.

In summary, the SSID is a crucial aspect of Wi-Fi networking, as it is used to identify and distinguish between different Wi-Fi networks. Understanding the role of SSIDs and how they work is important for anyone who wants to set up and manage a Wi-Fi network.