don't apologise............
viffing comes from the term "VIFF" or Vectoring In Forward Flight. When in forward flight the harrier's nozzles point backwards, however if the harrier gets a boggie on his tail, all the harrier pilot has to do is to turn, or vector, his nozzles down (this is extremely simple, they're all controlled by one lever) and the thrust will be directed downwards, just like when it hovers which is what in effect it's doing now. The attacking fighter pilot will not be expecting this, and has no choise but to carry on in forward flight. now the attacking fighter is in front of the harrier, if the harrier pilot puts the nozzles back he can carry on flying forward and he will now be on the tail of the boggie, i hope that explains it and ask if you're not sure about anything.................