It's like a tea that comes in all kinds of flavors and there are balls in it, they are tappioca.
I had one when I was in LA. It's pretty good but kinda a weird texture.
You don't know what bubble tea is? It's a tea drink originally from Taiwan, and spread through out the Pacific and North American coast. It comes in a variety of blended flavors, and has boba or jelly at the bottom. Boba itself is a slightly sweet, chewy, and has a round shape. Starbucks has a similar drink (without boba) that uses the same idea of combining green tea with cream or fruit flavors.