My son recently got into this.
You have to choose what liquid you want, then what you want in it. Also how sweet the liquid should be and how much ice.
Two main types of liquid - all cold - milky tea of various sorts, and luminous fruity clear liquids of a variety of technicolour flavours.
Then you choose what goes into it.
The original “bubbles” (boba) are tapioca pearls, that are individually swollen up in some kind of sweet brown sugary liquid, to the size of small marbles. They’re chewy - soft on the outside and firmer in the middle. Chunkier than the “tapioca pudding” of memory, and not a slurry - like a pile of chewy marbles. They’re disconcertingly filling. Weird, I can see why people like them but they’re pretty unusual and I didn’t really enjoy them that much. They come barrelling up the v wide straw and schluck into your mouth amidst the milky tea drink, like an inevitable recurring surprise.
Alternatively you can get the fruity bubbles, which are basically like edible versions of The Body Shop bath pearls c1992. They come in a lot of different fruity flavours and I think tend to be paired more with the fruity drink, so you can have orange mango tea liquid and green apple bubbles, for example.
Or, you can choose to have some sort of jelly cubes in the liquid. Or lumps of custard. Or other things. Basically there are a wide variety of things that they can put in the tea drink for you. And there’s the horrifying sounding cheese foam that can be added to the top - though as a pp said it’s apparently more like a cheesecake flavour than Stilton.
Worth trying, cos then you know what it’s like. But the places I’ve seen don’t look overly traditional, and it’s all so fake flavoured looking. Probably no worse than a syrupy Starbucks monstrosity though!