A balanced binary tree or a height-balanced tree is a tree in which the height of the left and right subtree at any node does not differ by more than one. Not just the root node, at any node. Mathematically we define using a balanced factor.
You have an internet connection. But what is an “internet connection” anyway? What is mobile data? What are WiFi, LAN, DNS, IP address, ISP, and lots of other jargon that you use or just ignore when you see them because you have no idea what it is?