Question

What is the difference between each of those urls ?

When will i use each ?

http://localhost/x

http://localhost:80/x

http://myComputerName/x

http://127.0.0.1/x

Answer 1

• http://localhost/x maps to 127.0.0.1 which is loopback. You can only use for
  local testing and can not give it to anyone on your network to visit
  the page.
• http://localhost:80/x is same as first because by default http works on port 80 and if you don’t specify the port 80 is asumed
• http://myComputerName/x can be given to others on your network because then they can connect to IIS on your machine (by resolving your host name) on port 80 and request x page/folder
• http://127.0.0.1/x is same as first. It is IP address equivalent of localhost.