Hows IPFS and Filecoin different? IPFS on Ethereum is Filecoin I believe. Currently IPFS is free, will there be a situation to pay for transaction and storage fees?
Filecoin is the incentive mechanism for IPFS. Currently the IPFS team, Infura, and people who are generous are providing public gateways but they often purge their caches frequently because there's no incentive to keep files permanently. Filecoin will change this because providers will be compensated for their storage by anyone who's willing to pay for their content to be stored long term.