1. is CubeFunds, and they are for adding worth to yours cubes.
2. is AccountFunds and they are only for buying items on site(cubes,membership,etc)
3. is EarningFunds and this is real money which you can actually withrdraw.
This is how actually looks cubes for real cash:
Link to register is www.you-cubez.com/
Now for the part where you can advertise here.
You can buy cube for 1£ and start with 0, or you can buy some cube that is on sale by other memmber an get a head start. That actually means that you can buy some cube for let's say 5£ that has in it some CubeFunds and what that means is that your cube will have more visitors since it is on first lets say 10 pages, and not on 500 page, what is case when you buy new cube. You can complete offers to get AccFunds and then buy cube, or you can get 5£ when you have clicked on 100 EarningFunds.
Not whery simple, but you can get more information on their forum.