Alice wants to buy Bob's Rolex, which they agree should take max 30 days to deliver. She sends 10k DAI to Unicrow's escrow and sets a challenge period of 30 days.
If Bob delivers what Alice ordered, he can claim the payment after 30 days. (Bob will earn positive reputation for a successful trade).
To improve her reputation, Alice can release the payment in advance after she receives Bob's parcel.