An Instalment agreement means a sale of movable property where the payment of the full price of the goods is delayed and is to be paid out in regular payments over an extended and agreed period.
The possession and use of the property is immediately transferred to the buyer, however, the seller remains the owner of the property and ownership only passes to the buyer on full and final payment of the price of the goods and when all the terms of the agreement have been met.
A lease agreement gives you the right to use an asset for an agreed period. During the agreed period of the lease you are obliged to make payments for the use of the asset as set out in the lease agreement.
At the end of the lease, you can either extend the lease or take ownership of the asset. If you choose to take ownership of the asset, there may be a final payment required depending on the terms of your lease agreement.