Unless a user requests and is paying for a static IP address, your Internet service provider temporarily assigns the user a dynamic IP address. The IP address is used for the duration of the Internet session. Once the session ends the dynamic IP address is sent back into the pool of IP addresses where it will be assigned to another user upon login. When you log back onto the Internet you will more than likely not get the same IP address. Since an ISP's customers are not using their services all at the same time, this cuts down on the number of IP addresses a consumer needs.
Static IP Address