Definition - What does Cydia mean?
Cydia is an application allowing users to download software on a hacked (known as jailbroken) iPhone or iPad. By using Cydia, users can search for apps in online repositories or in the Cydia Store. Most of the apps found in repositories can be downloaded for free, while most of those in the Cydia Store are for sale.
Techopedia explains Cydia
Normally, applications for Apple devices are downloaded via the App Store. However, Apple enforces strict guidelines, uses a rigorous process and charges a fee to developers. This is all done before developers are allowed to feature programs in the App Store. Some submitted apps are rejected.
Proponents of Cydia claim it provides an ideal environment for developers who want to create Apple applications, but do not want to go through Apple’s submission process. Cydia allows users to easily find these developer's Apple applications.
Before an iPhone or iPad user can download apps using Cydia, they must first have their devices jailbroken. Jailbreaking was once prohibited by Apple. However, a government ruling declared jailbreaking legal.
Anyone can set up a server and repository to be shared with the jailbreaking community. Once Cydia is made aware of the repository’s presence, it then adds the repository to its list. In effect, Cydia acts like an aggregator.