Unique Visitors: the number of different unique visitors coming to your website.
Each time a user comes to your website that counts as a unique visitor.
Example: if a user comes to your site, exits the browser or tab and comes back again using a new browser or tab all within 30 days that counts as 2 visits.
A single bot can be added to as many websites or/and landing pages as you'd like. The 'monthly unique visitors' will also be counted as a whole and not per site.
Engaged visitors: the number of people who hovered over or opened the bot.