An IP Address is the unique indentifier of a computer or device connected to the Internet. All devices on the Internet must have a unique IP Address in order to communicate with other devices on the Internet. When a device wants to communicate with another devices it will intiate a connection using the IP Address of the machine it is trying to connect to. If that address not reachable or not being used then it will fail to connect. Think of IP Addresses of telephone numbers. They are unique and can only be assigned to once person at one time.

IP Addresses are assigned to you by your Internet Service Provider whether you use a Dialup, Cable Modem, DSL, or T1 connection. These IP Addresses are either automatically assigned to your computer using DHCP or set onto your computer through your operating system.

If two computer on the same network are assigned the same IP Address, there will be an IP Address conflict. This could lead to erratic behaviour and loss of information. Usually your operating system will detect conflicts such as these and notify the user if it detects them.

Hostnames, such as www.bleepingcomputer.com, are always mapped to IP Addresses. These mappings are done using a service called the Domain Name System.