A mortgage deposit is a lump sum that the buyer uses to own a percentage of a property outright. For example, a buyer may pay 10% of the value of the property upfront and then borrow the remaining 90% through a mortgage lender.
Before you can 'exchange contracts' you will need to pay your deposit to confirm the sale. This is sent to your conveyancer who in turn sends this to the seller's conveyancer. Once you've paid this, be sure to give yourself a well deserved pat on the back for getting one step closer to owning your new home!