After getting an iPhone or iPad, first thing users usually hear is Cydia and second will be Installous. Cydia is app for iOS that enables user to find and install software packages (apps, interface customizations, system extensions) on a jailbroken (factory unlocked) iPhone, iPod Touch or iPad. Most of the apps available through Cydia are free but it also includes apps for sale through the Cydia Store. Most of these packages focus on providing customizations and modifications (tweaks) that can only run on jailbroken devices. To install Cydia you must jailbreak your iDevice. Here is how to jailbreak iPhone and install Cydia in simple way.