Too Long; Didn't Read
Your IP address on the Internet defines exactly where you are so that you can receive data. On the Internet, your ISP (Internet Service Provider) is responsible for assigning your network address and providing you with that address (which can be seen by the internet) Your home or computer network would be assigned a static IP address by your broadband service provider. The ISP allocate a different IP address every time you connect to the internet so to change the IP address while using dial up modem you can simply change your IP address.