Email leads are people whose email address you’ve collected through an opt-in form (with their permission). Marketers often collect email leads with the goal of later converting those leads into paying customers.
Email leads are often the first point of conversion in a customer journey. Because it is relatively easier to get an email address than a paying customers, marketers entice people to sign up for email lists as a way to make initial contact. Once a contact has joined an email list, it is easier for marketers to reach them with materials intended to nurture them from leads to paying customers.