There are two methods to assigning IP addresses to computers: dynamic and static.

Static IP addresses are used primarily for servers so that they don't appear to "move" while non-servers are usually assigned dynamic IP addresses. Most dynamic IP address users are users of internet service providers (ISPs) since not all the users of an ISP are online at one time and the ISPs can "get away" with not having enough IP addresses for each user.

In order to use a dynamic IP address, a service such as Dynamic Host Configuration Protocol (DHCP) is used to assign addresses dynamically to devices as they request them. If a static address is used, it must be manually programmed into parameters of the device's network interface. (It is also possible to "fake" static IP address assignments through DHCP by assigning the same IP address to a computer — and no other — each time it is requested.)