Ad Credits are the internal currency of the AdBit ecosphere. We use Ad Credits for our faucet and in our #LoveAdBit Forum. One AdBit Credit equals one Satoshi, i.e. Ad Credit is more or less like a Bitcoin but it's much easier for us to deal with Ad Credits.
If you for example earned 3 Million Ad Credits on our #LoveAdBit Forum by contributing content we credit those Ad Credits to your AdBit account. You can use those Ad Credits to buy ad spaces on websites or to pay for network bids.