WEP key

Definition
A WEP key is

"a series of letters, digits, and other characters that is used to limit access to wireless networks."

Overview
A wireless access point can be configured to require all computers attempting to connect to it to use a WEP key. When a computer attempts to join the wireless network, it must provide the same WEP key as the one stored in the access point. Users should set a WEP key that is long and complex, making it hard for others to guess. This should help to prevent people in close physical proximity to the access point from gaining unauthorized access to the wireless network.