WEP is a security protocol for Wi-Fi networks. Since wireless networks transmit data over radio waves, it is easy to intercept data or "eavesdrop" on wireless data transmissions. The goal of WEP is to make wireless networks as secure as wired networks, such as those connected by Ethernet cables.
The wired equivalent privacy protocol adds security to a wireless network by encrypting the data. If the data is intercepted, it will be unrecognizable to system that intercepted the data, since it is encrypted. However, authorized systems on the network will be able to recognize the data because they all use the same encryption algorithm. Systems on a WEP-secured network can typically be authorized by entering a network password.