Holding payment with a neutral third party that releases it when agreed work is accepted, so neither side has to trust the other with the money first.
It solves the standard first-project deadlock: the client does not want to prepay a stranger, and the vendor does not want to work unpaid. Both risks move to a third party.
We work with escrow and with staged payments tied to accepted milestones. Either is reasonable; what matters is that acceptance criteria are written down before the work starts.