What is contract of sale with right to Purchase?

It is best defined under this provision:

Article 1601. Conventional redemption shall take place when the vendor reserves the right to repurchase the thing sold with the obligation to comply with the provision of Article 1616 and other stipulations which may have been agreed ipon. (1507)

-      It is the right which the vendor reserves to himself, to reacquire the property sold provided he returns to the vendee the price of the sale, expenses of the contract, any other legitimate payments made therefore, the necessary and useful expenses made on the thing sold and fulfills other stipulations which may have been agreed upon.