Ubiquiti USW-WAN WAN Switch connects two Shadow Mode High Availability UniFi Gateways to a single internet service provider. It is designed for this WAN connection role in a UniFi gateway setup.
The switch uses 10G SFP+ connectivity to link the two gateways. This gives the specified high-availability arrangement a shared connection to one ISP. For a deployment with multiple ISPs, Ubiquiti specifies using an additional USW-WAN switch.
It is a focused networking component for connecting the gateways and ISP as described, rather than a general-purpose access switch.