One of our addresses has four parts: IP, port, username and password. The port depends on the protocol: 20001 for HTTP and 20481 for SOCKS5. What changes between tools is the order those parts are written in.
The four formats
The default is ip:port:username:password. The second puts the username and password first, username:password@ip:port. The third is a URL, with http:// or socks5:// in front. The fourth carries only ip:port, for whoever authorized the IP and uses no password.
The formatter converts from one to another and tells you which line it did not understand, instead of dropping it quietly. On the service page, the chosen format applies to the whole list and to the copy button.