Sales users are Marketing Cloud Account Engagement users who have access to the prospect database and can send one-to-one emails to prospects, but not list emails. Sales users can also view and edit prospect records, create tasks and activities, and sync prospects with Salesforce. You can set up sales users in Marketing Cloud Account Engagement by assigning them the Sales role and enabling the one-to-one email option in their user settings. Reference: [User Roles], [Create and Edit Users]