-> WPA 2 (Wi-Fi Protected Access version 2) Is the most secure means of Wi-Fi access. It has been available since 2006. If you have a home Wi-Fi router, you should turn on WPA 2. -> WPA (Wi-Fi Protected Access) Has exploits that can be break through its security. If WPA 2 is not available, you can feel reasonably safe using a WPA network.
->WEP (Wired Equivalent Privacy) Encryption has been exploited so much that it's like having no encryption at all. If you must use a WEP network, you should treat this wireless network as unsecured.
->No Encryption (Unsecured) Should be used with extreme care. The "open Wi-Fi" networks that are found at public hotspots could allow others on the same network to hijack your browser and view E-mail or social network connections.