I started the site with content aimed at developers, not the general public.
As there is a fair amount of traffic for people who are interested in using the equipment vs developing for it, I'll probably section off some of the site into appropriate content for each.
Currently thats in process.
In the interim - some of the answers -
GIT is a software tool for sharing source code to software.
UI is user interface (the stuff you click on to make things go).
iPKG is a tool for downloading more software into a device.