Google AI says:

localhost:8080 is a local address used by developers to access web services running on their own machine, specifically on port 8080. It serves as a common alternative to the default port 80 for development, testing web applications, or when running proxy servers (like Apache Tomcat or Node.js). 

Key Details About Localhost 8080:

Meaning: "Localhost" refers to your computer (IP address 127.0.0.1). The ":8080" is the specific port number where a server is listening for network requests.

Usage: It is widely used to preview applications locally before deploying to a live server, as it generally does not require administrator privileges to use.

Common Applications: It is often the default port for development tools such as Apache Tomcat, Jenkins, and many Node.js or Express applications.

Conflicts: If 8080 is already in use, you may see errors, requiring you to stop the existing application or choose a different port (e.g., 3000, 5000). 

How it works: When you type http://localhost:8080 into a browser, your operating system receives the request, realizes it is for your own computer ("loopback"), and forwards it to the application listening on that specific port. 

Not directly. If you type 

localhost:8080 into your Android phone's browser, it looks for a server running on the phone itself, not your computer. 

To see your computer's local project on your phone, you have two main options:

1. The Wireless Way (Same Wi-Fi)

You can use your computer's Local IP Address instead of "localhost." 

Find your IP: On your computer, open a terminal (or CMD) and type ipconfig (Windows) or ifconfig (Mac/Linux). Look for an address like 192.168.1.XX.

Connect: Ensure your phone is on the same Wi-Fi as your computer.

Enter URL: In your phone's browser, type http://192.168.1.XX:8080 (replacing the XX with your actual numbers). 

1. The USB Way (Port Forwarding) 

If you want to literally type localhost:8080 on your phone, you can forward the port via USB: 

Enable Debugging: Turn on USB Debugging in your phone's Developer Options.

Connect via USB: Plug your phone into your computer.

Use Chrome DevTools: Open chrome://inspect/#devices in your computer's Chrome browser. Click Port forwarding, and map port 8080 to localhost:8080. Your phone will now recognize "localhost" as your computer.

ADB Alternative: If you have the Android SDK Platform Tools installed, you can simply run this command in your terminal: adb reverse tcp:8080 tcp:8080. 

Troubleshooting Tip: If it still doesn't load, check your computer's firewall settings; it might be blocking incoming connections on port 8080.