MUV stands for Monthly Unique Visitor. A monthly unique visitor is an individual user who accesses your site within a 30-day window. The unique visitor is determined by a cookie that lasts for a period of 1 year or until users clear their browser cookies for websites.
For mobile apps, the equivalent is a monthly active user - an app user who opened your app at least once within the 30-day window. A unique app user is determined as the unique instance of the app installation until the user's app data is cleared or the app is uninstalled.
On the Sprout plan, there is a hard limit of 10,000 MUV per account. On Blossom, Garden, Estate, and Forest, your account will not be charged anything for up to 100K MUV, 200K MUV, 300K MUV, and 400K MUV respectively on a per-agent basis. Once your MUV limit crosses the respective initial limit, your account will be charged $39 per month for every additional 100K. Let us look at some example cases:
CASE 1: You are in Blossom Plan and your current MUV/Agent is 80K -> you are not charged anything
CASE 2: You are in Blossom Plan and your current MUV/Agent is 250K -> you will be additionally charged $78 for the account ($39 for 100-200K and another $39 for 200-300K)