Just search leadcore, it's controversial - some for and some against; vehemently so. It's only been a short while since the last one.
Helicopter is your hook-link coming off your main line via a ring (of some description) with your lead at the end of your main line; the same as a chod really, or even a paternoster. It's just alternative ways of viewing it [the "rig"], lengths of hook-links, length from where the hook-link is in relation to the lead...
Sorry if I've confused you even more.