Product Details:

Ethernet was originally created for the LAN (Local Area Network) and not for the WAN (Wide Area Network), one of the reasons was the distance limitation that the first Ethernet standards offered.
The technology of Ethernet is used a lot in networking products, which makes it cheap to produce Ethernet products compared to other networking technology. This is one of the reasons why Ethernet is interesting to use outside of the LAN.
Metro Ethernet was first used outside of the LAN in metropolitan areas, called MANs (Metropolitan Area Network). We use fiber cabling because of the support for longer distances. Here are some of the standards that are suitable for Metro Ethernet:

Name	Distance	Bandwidth
100Base-LX10	10 Km	100 Mbps
1000Base-LX	5 Km	1 Gbps
1000Base-LX10	10 Km	1 Gbps
1000Base-ZX	100 Km	1 Gbps
10Gbase-LR	10 Km	10 Gbps
10Gbase-ER	40 Km	10 Gbps
40Gbase-LR4	10 Km	40 Gbps
100Gbase-ER4	40 Km	100 Gbps

As you can see in the table above, we can now cover distances of up to 100 Km (62 miles) and up to 100 Gbps.
Metro Ethernet was first only used in metropolitan areas, that’s why it’s called “Metro” Ethernet. Nowadays it’s also used for long-distance WAN links, often named Carrier Ethernet. From the customer’s perspective, it’s like you are connected to a regular switch:
On the customer’s side, you get an Ethernet connection that you can connect to your router, switch or firewall. The provider will use switches on the edge of their network. The technology that is used inside the provider network is unknown to the customer. This could be something like MPLS. Ethernet frames that are sent by the customer router on one end, will be transparently transported to the other end.