Resolved Second IP address

You can have a local IP address for each network adapter. e.g. 192.168.1.x

You can have multiple WAN IP addresses too. One address will be provided by your ISP and you can lease additional addresses from the ISP. Useful if don't use a router, you need a switch instead and the modem will route to each pc. But it's cheaper to use a router, one WAN IP is all that's needed.

A server computer could have 2 network adapters. One used for Internet and one used for the local network. All local computers route through the server to get to the Internet. The server could provide security, firewall, site access restrictions, antivirus, local IP addressing, etc. Most larger business networks are setup like this.

It gets complex where one has to "bind" the network adapters to specific services, as in databases, Web applications, email distribution systems, backup tasks, etc.

For a home pc, there's no need for additional IP addresses. In fact, Windows (non-servers) can only use one IP address at a time, even if have multiple network adapters. For example, you could connect by wire to your wired network and at the same time connect by wireless to a neighbor's network. Windows will use the one that connected first and the second connection will be ignored (useless). Thus, if the wired connection was established first, you could not use the wireless connection until the network cable was unplugged.