HENkaku is the first ever homebrew enabler for PS Vita and PSTV. It is akin to jailbreaking your iPhone or rooting your Android device.
HENkaku Development Wiki
The HENkaku Development Wiki (where you are right now) is a site with lots of information about how HENkaku, and the PS Vita in general, works. Despite being outperformed by the PS Vita hacking and homebrew community with their SDK, the HENkaku Development Wiki is still being used today by many people from around the globe.