Ritvik clicked 'yes' on an offer on a website. This act of Ritvik accounts to:

Acceptance

An assent or consent given to an offer by the offeree is known as Acceptance [Section 2(b) of Indian Contract Act]. By saying 'yes', 'ok' or clicking on 'I agree' on an offer on a website also amounts to acceptance. An offer when accepted becomes an agreement. An agreement is also called as promise.