A better example of the shield generator would be the shield that protected the rebel base on hoth. (regional shield)
In essence the generator is there to protect cities on a planet from bombardment or intrusion. The projector is indeed like said the shield that protected the death star, its function is to protect a space station in obit or perhaps close to orbit?
But right now only shield generators are already working in the game.
All the answers you were given (except Retto's) were the same and were correct. A generator protects an area on the ground (and is implemented) and a projector "projects" a shield to boost the shield power of a space station (or perhaps a ship) in orbit (and is not currently implemented).