What is Jailbreaking?
Jailbreaking is basically the process of freeing your device (thus the term jailbreak) from the limitations that are imposed by Apple. While the iOS is one of the most stable and secure mobile operating systems around, it can become too restrictive due to Apple's "closed" mantra. Jailbreaking will allow the user to have read/write access to the iOS operating system which allows them to download and install additional apps, extensions and themes that are all unauthorized by Apple and not available officially in the App Store. And this brings us to the next important topic which is Cydia.
Cydia
Of course, you can't discuss about jailbreaking without mentioning Cydia. This is essentially the ultimate reason why you jailbreak your device. One can say that there is no point to jailbreaking your device if you don't even want to install Cydia. Jailbreaking your device will install Cydia into it which is a third-party digital distribution platform. To keep it simple, think of it as the "other" App Store or the "black market" version of the App Store because in a sense, all unauthorized apps and tweaks usually end up here. Much like the App Store, there are both free and paid apps (referred to as packages) available in Cydia.