There is no tea in it, not even "herb", yet it's called "milk tea". Some people would add some red tea into it. But I don't, thinking tea doesn't yield significant flavor in such a blend.
Fruit milk tea is a seriously important thing in Taiwan. Once I had a Taiwan roommate and we made fruit milk tea every summer afternoon. We always skip the "boba" or "pearls" (little starch balls commonly added to milk tea) and only use fruit and milk. I love all kinds of fruit milk tea, even apple has a different taste when made into milk tea. But mango is one of my favorites. Papaya is another of my favorite. Strawberry is good too, but I always find the strawberry seeds annoying. Kiwi is nice and interesting. When blended, it (probably its seeds) has a hint of peppery flavor along with the normal kiwi taste. We also used cantaloupe and honeydew melons sometimes. Sometimes we blended in banana to sweeten the beverage. But these days I seldom use banana. For some reason, banana blended in milk tastes very sweet to me, almost too sweet for me to handle.
Making mango milk tea is very easy. Usually I use one of this kind of yellow mango (or two, if they are really small), two glasses, and 1.5 glasses of milk.
The Mango is sliced into small pieces, and completely homogenized with milk in a blender.
There are a lot of milk tea shops in China. I've seen some milk tea shops in the States too. The best shops always use real milk and real fruits. And when they do so, usually they have their blender and fruits displayed on the front counter. In China, milk is more expensive than a lot other things. So some shops use milk powder, condensed milk or condensed cream as the base of the beverage. Of course it can never be as good as real milk. In the States, fruits are relatively expensive. I've seen some shops using flavoring powders or flavoring liquors to yield fruit flavors. Most of them don't taste awfully bad, but can never be compared to real fruits. If a fruit milk tea doesn't use real milk or real fruit, I would rather skip it. So when I walk into a milk tea shop, I always look for their blender and fruits displayed somewhere up to the front. If they are there, then very likely the fruit milk tea is the real thing.
There can be things added to fruit milk tea with a lot of options such as honey, sugar, ice, "starchy pearls", tea, whipped cream, vodka... But basically, the secret to a good glass of fruit milk tea is simple - real, fresh milk and real, fresh fruit.