An IP address is a unique number assigned to you whenever you connect to the internet. Without an IP address you would be unable to surf the Internet or send and receive email. It would be a bit like trying to use your home phone without having a telephone number.
When you turn on your router, it will automatically connect to your broadband service. When it does this it will be given an IP address, there is no need to enter this yourself.
No, each time your router connects to the broadband service you will be given a new address. This is known as a dynamic IP address. We do not offer static IP addresses, where your IP address would stay the same each time you connect.
You may have heard IP addresses being referred to in this way. This is because your router will actually have 2 IP addresses. It has one that it uses to speak with other computers over the internet (external) and another that it uses to speak with devices within your home (internal).
All TalkTalk routers have an internal IP address of 192.168.1.1 by default. To find out your external IP address please see How do I find my IP address.