localhost is a loopback addresses in which the IP point to your computer. A loopback address is a special IP address reserved for use in testing network cards that always looks like 127.x.x.x and it needs a network interface to communicate with itself (via: LAN, WAN, etc.) see the difference
How is an address used for testing network cards applied to testing websites? With HTTP software, the loopback address connected to the internet becomes a web server capable of serving your HTTP responses and sending HTTP requests to other servers. On the other hand, with local server software, a server can communicate across its local network without an internet connection.
The difference between local and web servers is predominantly the software a server is running. They both function is similar ways but the communication path varies.
For example, Express.js creates an http server utilizing Node’s http core module and it then listens to the specified port for incoming requests and sends back your response. Express is built on top of Node’s http module and with that being said a similar configuration can be made with Node explicitly or the many other Express alternatives.
resources: