The Guest Pass app page sums it up: "Do you share passwords with people to join your Wi-Fi network on a regular basis? Guest Pass makes this easy. Just fill out the simple questions in Guest Pass and e-mail the resulting Guest Pass without ever leaving the app. Users receive an attachment that they tap [iOS] or click [OS X], and the next time they are near your network, their iPhone, iPad, or Mac will automatically connect. You can also set expiration dates so the settings will be deleted [from] the device on the expiration date." The way it works is that a special, encrypted configuration file is sent to the recipient who must be using iOS 5 or later or OS X 10.7 or later. The recipient will never see your network password. You can set an expiration date, but if you want to provide semi-permanent access, you set set an expiration in the far distant future. Using Guest Pass provides finer control over who and how long access is allowed than the "Enable Guest Network" found in the Apple AirPort Utility.