Bitcoin is censorship-resistant money. Anybody can send money by broadcasting a transaction to the network. After broadcast, transactions are packaged up into blocks by miners. Miners compete against other miners for the privilege of building on the chain. This is what keeps bitcoin decentralized.
Satoshi Nakamoto, the pseudonymous inventor of bitcoin, also mined the first bitcoin block. He left the world a secret message in the very first bitcoin transaction that was ever made. Your first challenge is to find and decode it.