Such companies offer a wide variety of unmoderated matchmaking services, most of which are profile-based.
Online dating services allow users to become "members" by creating a profile and uploading personal information including (but not limited to) age, gender, sexual orientation, location, and appearance.
Ok Cupid is free to join, free to search, and free to message.
As a Christian dating site we believe that marriage is a sacred covenant between man and woman, ordained by God as part of His divine plan for each of us. God says in Genesis : "It isn't good for man to be alone; I will make a companion for him, a helper suited to his needs." God himself brings people together according to his timetable.
That is, online dating sites use the conceptual framework of a "marketplace metaphor" to help people find potential matches, with layouts and functionalities that make it easy to quickly browse and select profiles in a manner similar to how one might browse an online store.
Under this metaphor, members of a given service can both "shop" for potential relationship partners and "sell" themselves in hopes of finding a successful match.
Still others rely solely on paid membership subscriptions.