The WAN ethernet looks like the above picture.
It has both the Small Form-Factor Pluggable (SFP) on the right for fiber, and copper (RJ-45) Gigabit Ethernet connectivity
Either the SFP port (operating at 100/1000 Mbps) or the RJ-45 (operating at 10/100/1000 Mbps) port can be active at one time.
Built in ethernet is part of the chassis, and not on a separate module, like the picture above.
IP addresses can be assigned to either type of interface, built in or added as a port on module, and will be routed ports.
Ethernet is pretty much still ethernet.
WAN ethernet ports - probably are for MPLS links; which are WAN technology;
There are 2 LAN Ethernet ports in Cisco 1841;
see the middle small picture
Ethernet is Ethernet. Nowadays a router normally has one or more Ethernet ports. It is possible to add more Ethernet ports using additional modules these can be HWIC or Network Modules (NM). There will be a mixture of copper RJ45 or SFP which allows you to choose copper, multimode or single mode fibre connections. Some ports can are limited to layer two and others are layer two or three. The important point is they are all Ethernet so generally the concept of LAN and WAN does not exist. Telcos will present an Ethernet circuit to you as copper (which you might have to cross over) or fibre but behind the scenes they may be carrying the Ethernet over another technology.