Bubble tea is invented in Taiwan in early 80s and it is a national drink of Taiwan. The bubble tea was introduced to Japan in late 90s and now it is a big boom in Japan. If you see a long queue in front of a stand in Tokyo, it should be a queue waiting to buy a bubble tea.
However, the name, bubble tea is not known to Japanese. Japanese use Tapioca tea or Tapioca milk tea instead of bubble tea. Therefore if you talk to Japanese, please avoid using bubble tea. By the way, tapioca is a starch extracted from the storage roots of cassava.
There are many types of bubble tea and may be it is hard to choose but if you try for the first time, better to try the cheapest one and decide if you want to order again. Usually the cheapest one is the most standard one.