What is a resolutory condition?

Article 1181 of the Civil Code of the Philippines provides:
ART. 1181. In conditional obligations, the acquisition of rights, as well as the extinguishment or loss of those already acquired, shall depend upon the happening of the event which constitutes the condition. (1114) 
A resolutory condition (condition subsequent) extinguishes the obligation upon its fulfillment. The obligation is demandable at once, without prejudice to the effects of the happening of the event.[1] Before the fulfillment of a resolutory condition, the preservation of creditor's rights applies.[2] After the fulfillment of a resolutory condition, Whatever may have been paid or delivered by one or both of the parties upon the constitution of the obligation shall have to be returned upon the fulfillment of the condition [3]. There is no return to the status quo. However, when the condition is not fulfilled, rights are consolidated and they become absolute in character.

[1] Paragraph 2, Article 1179, Civil Code.

[2] Paragraph 1, Article 1188, Civil Code.

[3] Paragraph 1, Article 1190, Civil Code.