What is Bitcoin?

You ask: What bitcoin?

Bitcoin is money made of computer numbers, no chief control it. Normal money, big chief tribe (bank) keep tally of who own what. Bitcoin keep tally on giant shared list instead, called blockchain. Thousands of computers each hold same copy. When Caveman send bitcoin, all computers write it in list — hard to cheat, because cheater must fool most of tribe at once. New coins made by mining: computers race to solve very hard number puzzle. Winner add next page to list, get fresh coins as prize. Every four winters that prize cut in half, so new coins come slower and slower. Puzzle keep list honest — changing old page mean redoing all puzzles after it. Only 21 million coins can ever exist, so no chief can make more. Caveman own coins with secret key. Lose key, coins gone forever. Cave wisdom: bitcoin is tally rock whole tribe watches, so no one chief can lie.