Adverts are uploaded by corporates looking for publicity for a fee and a budget. Its a pay per watch metric. Daily users log into their accounts to watch adverts and for every successfully watched adverts, they receive some fuel tokens in their wallets. To increase the value of the received tokens, they burn the fuel by moving around to keep fit. The tokens then gets converted into full value rewards in USDC once they completed the daily milestones (usually above 10000 steps)