Email lists are lists of constituents and their email addresses that are used to send emails using the Email Marketing module. An email list is typically a segmented group of constituents that will receive a specific type of communication from you (such as recent donors, volunteers or board members). A constituent must have a primary email in order to be added to an email list.
You can edit the email lists a constituent is subscribed to from the profile page by clicking the the white space and choosing an email list to subscribe to. You can also remove a constituent from an email list by clicking on the 'X" next to the list name. Be sure to click on Save to save the changes for the constituent.