'localhost' is the DNS name of the IPv4 address 127.0.0.1, which is reserved on every computer system to point to itself. DNS lookups, if you type http://domain.com in your browser or any other app on your computer, or if you type http://localhost, are translated by your operating system. It first looks in a so-called hosts file (/etc/hosts on linux and on windows in C:\windows\system32\drivers\etc\hosts (mind you, the 'etc' folder might be hidden but you can type the path in the address bar). You need administrator rights to change these files, but you can add a translation yourself in there. Every line is 'ipaddress<space>domainname1<space>domainname2' where domainname2, 3, 4 etc are optional if they point to the same ipaddress. If you forgot you edited this file, websites may start behaving badly, so be careful. If the domain is not found in the hosts file, the computer goes up the network to it's closest DNS server, and if this server does not know the domain, it contacts it's parent and so on, until the IP address is found that goes with a domain name, and this is send down the chain to the requesting computer. Google for more information on this topic if interested. Every computer has the '127.0.0.1' ip address, which is only available on the local system, because on another computer this number points to the other computer itself. If you need other computers to be able to contact your local computer, you have to find out what the network IP is of your computer, or maybe even the external internet address of your router and do port forwarding. Google these terms if needed as well. See also https://en.wikipedia.org/wiki/Localhost If you want more help, post all used technologies: linux/windows/mac, which webserver and database, what are you expecting and seeing, where did you put localhost and how are you accessing your site? What errors are in the logs?