It’s a way to trade – to buy and sell things – without official currency.
Mortgages, savings accounts and (sometimes) current accounts; owned by their members.
Currencies (like Bitcoin, for example) controlled by blockchain technology, not corporate banks.
Use currencies that stay in your local community, instead of being sucked out by corporate branches.
Invest in land co-ops, community energy etc. for a better return than from a bank savings account.
Local co-operative savings & loan schemes: an alternative to loan sharks.