What is the purpose of the blue WAN port on the back of some routers?

What is the purpose of the blue WAN port on the back of some routers?
The blue WAN port on the back of some routers is used to connect the router to a Wide Area Network (WAN) such as the internet. The WAN port is typically labeled as such and is often distinct in color from the other ports on the router.

When connecting to the internet, the WAN port is used to receive a signal from an internet service provider (ISP) modem or other device that provides internet connectivity. The router then distributes this signal to the other devices on the local network, such as computers, smartphones, and other devices, via its other ports, usually labeled as LAN (Local Area Network) ports.

In summary, the blue WAN port is the gateway for internet connectivity and serves as the interface between the router and the ISP modem or other internet service provider device.