Conventional Guaranty, Legal Guaranty or Judicial Guaranty,  Gratuitous Guaranty, or Guaranty by Onerous Title

Art. 2051. A guaranty may be conventional, legal or judicial, gratuitous, or by onerous title.
 
It may also be constituted, not only in favor of the principal debtor,  but  also  in  favor  of  the  other  guarantor,  with  the latter’s consent, or without his knowledge, or even over his objection. (1823)
 
Art.   2052.   A guaranty  cannot  exist  without an valid obligation.
 
Nevertheless,  a  guaranty  may  be  constituted  to  guarantee the performance of a voidable or an unenforceable contract. It may also guarantee a natural obligation. (1824a)
 

GUARANTY IS AN ACCESSORY CONTRACT

>     It  is  indispensable  for  its  existence  that  there  must  be  a principal obligation
>     So if the principal obligation is void, it follows that it is also void
 

A GUARANTY MAY SECURE THE PERFORMANCE OF 

1.   A  voidable  contract  inasmuch  as  such  contract  is  binding unless it is annulled by a proper action in court
2.   An unenforceable contract because contract is not void
3.   A  natural  obligation  so  that  the  contract  may  proceed against  the  guarantor  although  he  has  no  right  of  action against the principal debtor for the reason that the latter’s obligation is not civilly enforceable