An MQL is a marketing qualified lead and an SQL is a sales qualified lead. An MQL is a potential lead that has expressed interest in your company and/or has the right general characteristics of your target audience, but they need to be further qualified. Marketing teams will send MQLs to their sales team who then engage with them to determine where they are in their buying journey. The sales team will then qualify that lead as an SQL if they should be further pursued or nurtured.