Apple AppStore provides many more apps to download for iOS devices like iPhone, iPad and iPod touch. But Apple enforces strict guidelines, and they charge form developers.sometime they don't accept all working apps to include an apple app store.
What is cydia
Overcoming this situation, Cydia becomes a good environment for new iOS developers. Because Cydia does not ask any submission process, the developer can develop any kinds of iOS apps. But you cannot install those app directly like apple app store apps.
You need to jailbreak your iOS device and install Cydia app. Cydia app cannot connect without jailbreak. because when this jailbreak iOS device, Cydia app get that root access to your iOS device which enables full admin access to your iOS system Which mean, you can customize any features as you want.
What is Cydia source
Once you have jailbroken your iOS device, Cydia app will installed automatically. Then you can search for many apps and tweaks from Cydia search. But you cannot get many more apps from there because you need to add Cydia package/ source to your Cydia app.Cydia sources consists of many more apps and tweak, there for you need to add best Cydia tweak to your Cydia. There are many more Cydia sources available. Each of sources is different from other.
When you add Cydia sources to your Cydia, make sure to choose the right one for you because there are many nonuseful Cydia sources available. Hope this article helped you to get to know about what is Cydia and Cydia download.