Visitors is a feature that allows you to see which of your matches have viewed your profile page within the last 2 weeks. Once you have purchased a subscription, this information will be available on your Dasbhboard under the Visitors tab. If a match views your profile multiple times in one day, your view history will only show one view of this match.
Also, If you are a new member or have not been very active, you may not have many views of your profile yet. Just as with communication, eharmony encourages you to give your matches time to view your profile. Completing and updating your profile and posting photos will help you get more views and communications.