A lan port is a network port of a local area network connection that is used to share files and data between connected devices and as an access point that connects computers and other devices to the Internet. Lan ports enable computers to connect to the ethernet lan, MAN (metropolitan area network), or WAN (wide area network). Compared to MAN and WAN, lan connects multiple devices over a short distance.

For instance, in a manufacturing plant, computers, machines, and devices on the same lan can quickly share files and information with each other and devices like printers. Commonly, you can easily create a small-sized lan with a router that has around four to eight lan ports. However, for enterprise level that needs a huge local network, you can change your router with a network hub or a switch made to handle more lan ports that connect to various devices.

RJ45 is a lan port that uses RJ45 ethernet cables. RJ45 or Register Jack-45 is a standardized interface often used for connecting computers onto Ethernet-based local area networks (lan). Simply said, RJ45 is the plastic connector head located on both ends of a lan cable.

The physical look of a lan port and a WAN port can be identical with the same RJ-45 ethernet port. However, some differences between lan and WAN ports really separate these two network ports. A Wide Area Network or WAN port connects devices with an external network that covers a vast area across national and international borders like the Internet. Therefore, typically, there is a WAN port and four lan ports in a router. The lan ports share the internet connection from the WAN with all connected devices such as computers, printers, and IoT devices. 

Another differentiator between lan and WAN ports is the difference in data transfer rate. lan ports have a higher data transfer speed compared to WAN ports. For instance, lan ports speed can reach up to 1000 Mbps compared, and WAN ports can only be up to 100 Mbps.

In computers, lan ports are connected to the device's motherboard through a NIC (Network Internet Controller). NIC often has different specs and brands, and you can change them with a different type of NIC depending on your computer's needs. Other common locations of lan ports are located in switches, network hubs, modems, and routers. Connecting devices into lan requires an Ethernet cable to connect two lan-compatible devices. Connecting your lan devices with an Ethernet cable into a router or modem that is connected to a WAN will enable your device to access the Internet.