In simple terms every time you fly with Virgin or one of their partner airlines, you will be awarded a certain number of miles for your outbound & return flights.
Each person must claim their "own" miles, ie. you can't claim for other people in your party who may not be members of the FFC.
Once you have banked a few miles you can go to the Virgin Atlantic site & click the link for "miles plus money" ... It will give you a reduced price for the flight depending how many miles you have banked that you want to exchange.
My friend has done this recently, and the price was good, BUT he had to do it seperately for each member of his family using their FFC accounts..
The system said seats were not available for all of them & he ended up talking to VA customer services to get it all sorted out..
As a member you will get e-mails offering you specials such as flights for half the usual miles, but we are still talking 22,000 plus miles for one of these free fares!
I have been collecting for some years & just have enough myself for one now..
The other thing you can do is put them towards upgrading to the next class ie premier or business..
All in all a good scheme, but like I said keep an eye out for specials..
Hope this helps, Hazel