Some sites provide free registration, but may offer services which require a monthly fee.
Other sites depend on advertising for their revenue.
Sites may offer additional services, such as webcasts, online chat, telephone chat (VOIP), and message boards.
Some sites such as Ok Cupid.com, and are free and offer additional paid services in a freemium revenue model.
Some sites are broad-based, with members coming from a variety of backgrounds looking for different types of relationships.
Other sites are more specific, based on the type of members, interests, location, or relationship desired.
Online dating sites use market metaphors to match people.