Stands for "Personal Area Network." A PAN is network of connected devices used by one person. It allows devices such as computers, tablets, smartphones, and smartwatches to communicate with each other.
A PAN may incorporate a number of different connections, including Ethernet, Wi-Fi, and Bluetooth. For example, a desktop computer may connect to a personal router via Ethernet and a tablet may connect via Wi-Fi. A smartphone may communicate with a computer via Wi-Fi and a smartwatch via Bluetooth.
Since PANs are designed to be limited to a single user, they are often secured automatically by only accepting connections from authorized devices. However, it is wise to double-check your connection settings to make sure that a password is required or that only authorized devices can connect, rather than "everyone."