Around & Around We Go (Circulating Supply)
Circulating supply is the token supply that are available for trade on CEX or DEX. There are non-tradable tokens such as vesting tokens for early investor, tokens in community funds/treasury etc. For $LUNA, there are max supply of 1B (some says $LUNA has no supply cap or dynamic supply. I can't find info on those yet) but circulating supply is at around 390M according to Messari.