There are private and public IP addresses.
All internet-capable devices will have a private IP address. Your router will generate private IP addresses as unique identifiers for each device to differentiate them on the network.
A public IP address will be used to recognize and differentiate networks. While each connected device has its own IP address, it will also be included within the main IP address for your network. Your public IP address is provided to your router by your Internet Service Provider. ISPs have a large pool of IP addresses that they distribute to their users.
Public IP addresses are either Dynamic or Static.
Dynamic IP addresses change automatically and regularly.
Internet Service Providers have a number of IP addresses and automatically assign them to their customers. The ISP will also periodically re-assign them to other consumers.
Static IP addresses are constant.
Once the network assigns a static IP address, it will remain the same. Most individuals and businesses will not need a static IP address, except where they host their own server. A static IP address ensures that websites and email addresses tied to it will have a set IP address.