An offer is a unilateral proposition which one party makes
to the other for the celebration of the contract.[3] Offer is a proposal made by one party (offerer) to another to enter
into a contract. It is more than an expression of desire or hope. It is
really a promise to act or to refrain from acting on condition that the
terms thereof are accepted by the person (offeree) to whom it is made.[4]
An offer is terminated if:
a. there is a rejection by the oferee;b. incapacity of the offeror or offeree before acceptance is conveyed[5];c. there is a counter-offer;d. lapse of the time stated in the offer without acceptance being conveyed;e. revocation of the offer before learning of acceptance; orf. supervening illegality before acceptance.

For an acceptance to be valid, it must be: (a) must conform with all the terms of the offer; (b) directed and communicated to the offeror and learned by him; (c) made within the proper time; and (d) communicated expressly or impliedly but it is not presumed.
[1] Article 1305, Civil Code.
[2] Insular Life v.
Asset Builders Corp., G.R. No. 147410 (2004).
[3] Tolentino. Obligations and Contracts.
[4] De Leon. (2014). Obligations and Contracts.
[5] Article 1323, Civil Code.
[6] Supra note 4.
[7] Malbarosa v. CA, G.R. No.
125761 (2003).