There are two different types of deposits: Security and Holding deposits. By clicking on the Deposit section under the Rental conditions, you will get more information about each type of deposit.
The security deposit is the amount you have to pay on move-in, directly to the landlord, to cover for any potential damages that may occur during your stay. The landlord may also keep the security deposit if you leave earlier than agreed.
If no damages occur, and you leave on the agreed move-out date, the deposit should be refunded in a way you both agree on.
The information about the deposit is stated in the Rental conditions section, and also in the booking request and confirmation emails.