Smart Connect is a feature on wireless routers and access points that broadcasts a single SSID over both 2.4 GHz and 5 GHz frequencies. It allows a Wi-Fi router to automatically assign wireless devices to the ideal frequency and channel and reassign devices when necessary.
Wi-Fi networks can operate over two separate radio frequencies: 2.4 GHz and 5 GHz. 2.4 GHz networks can operate over a longer range than 5 GHz, but 5 GHz networks have higher data transfer rates. Without Smart Connect enabled, a router needs to use a separate SSID for each frequency. Your computers and mobile devices will need to connect to and save each SSID separately if you want them to use both. A device will typically choose the network with the stronger signal when it tries to connect to a Wi-Fi network and will remain on that frequency until you disconnect it, regardless of whether the other one is stronger later.
With Smart Connect enabled, computers and devices only need to connect to and save a single SSID. When a device first connects to the wireless network, the router assigns it to the frequency and channel with the strongest connection at the time. As it moves around, and other devices use network bandwidth, the router will transfer it to the other frequency when necessary to maintain a strong connection. This allows the router to spread traffic across all available frequencies instead of letting one become overloaded while the other is idle.