A public IP address is a unique identifier assigned to a device connected to the internet. It allows devices to communicate with each other over the web. Public IP addresses are assigned by the Internet Assigned Numbers Authority (IANA) and can be either static (permanent) or dynamic (changing over time). These addresses are essential for routing internet traffic, enabling users to access websites and online services. Each public IP address is visible to anyone on the internet, making it possible for servers to send data back to the correct device. This visibility is crucial for activities like web browsing and online gaming.