Because IP addresses are limited, there is simply not always enough to go around. To make sure everyone is able to connect to the Internet, the system is separated into static IP addresses and dynamic IP addresses.
Static IP address
A Static IP address is designed to provide the user with a more stable identification. Think of this as a phone number. You have a standard phone number in which people can locate your phone and contact you. It remains the same unless you specifically decide to change it. A static IP Address works in much the same way, in that it is used as a permanent ID.
Dynamic IP address
A dynamic IP address is for the opposite. Think of it like a pay phone. It is a temporary identification to allow you to connect to the Internet. Just like a pay phone, though, you can only make “outgoing” connections. This will mean that you cannot accept incoming calls because the “number” changes when you disconnect. Even if you were to reconnect immediately, the chances of you receiving the same IP address is very small.
So, if your ISP (Internet Service Provider) delivers dynamic IP addresses (most of them do), your IP address is different every time you connect to the internet. This does not mean that your IP is hidden or that you are untraceable. Every ISP has a predefined range of IPs; so your IP address can be identified as belonging to your ISP. Plus, all ISP do log their traffic; so they do know they have allocated you a certain IP at a certain moment in time.
Even if you have dynamic IP addresses you need to hide your IP id you what to browse anonymously. The good news is that you have been banned from a forum or certain sites based on your IP you can create a new account with no problems.