The boba in boba tea is made from tapioca, which is a gluten-free starch extracted from the root of a cassava plant. The actual drink is made from a tea base mixed with milk and flavoring. Some boba tea places have certain teas that are seasonal, like at the bubblecup tea zone. Examples of some seasonal boba tea drinks is the pumpkin spice milk tea. Boba tea also has non-dairy drinks for people who are lactose intolerant like myself.
Poke' bop boba tea by Cynthia Smoot from Flickr.com liscensed for commercial use