The terms are used interchangeably, so you need to find out exactly what you have bought.
If you have bought in Mexico it is most likely a club membership as opposed to deeded ownership in real property. Its the loan that makes it more complicated, so check who that is with and if it is a formal loan set up in your country of residence, that may be more of an issue than just a final payment due direct to the seller.
While you have almost certainly been lied to extensively, you may find that the membership is useable by you, if you go to the resort and like it, so take some time to review whether it is something you can actually use effectively vs the disruption with defaulting at this point.