Denis,
A LAN (Local Area Network) connection refers to a network with implications that there is no Internet access. A WAN (Wide Area Network) connection refers to a network that generally has Internet access.
On your Conduit you will want your devices to connect to the Ethernet LAN and use a different interface (WiFi, Cellular, …) as the backhaul connected to the Internet. A WAN interface is the interface that typically has the default gateway configured.
The Conduit has the ConnTrak and routing modules to accept traffic and send it out on the Internet. With the use of static routes and firewall rules routing from the LAN to the WAN and onto the Internet can be restricted and controlled.
Jeff