Cargo credits are digital tokens that you swap to create collectibles. One collectible creation equals one Cargo credit. That means if you have 500 Cargo credits you can create up to 500 collectibles at once!
When you first sign up for Cargo you get a free Cargo credit on the house. You will still need to pay the gas fee to submit the transaction on Ethereum.
You can also purchase Cargo credit packs to fuel your project. You can purchase a credit pack from your dashboard by clicking on the green "Buy more" button in the header on desktop and within the menu on mobile.
Cargo credits are ERC-20 tokens within Ethereum. That means that unlike traditional credits systems you actually own these credits and can transfer them to other Ethereum addresses. You could even sell them on secondary markets or trade them for stuff that you like! When you redeem a credit you are submitting a transaction on the Ethereum blockchain and everyone pays their fair share. So when you redeem a credit you will be asked to include a small (usually a few cents) gas fee to power your transaction. People need to store this data after all.