The BTC ticker stands for Bitcoin.

Bitcoin is a digital currency and a payment system invented by Satoshi Nakamoto. The system is peer-to-peer; users can transact directly without an intermediary. Transactions are verified by network nodes through cryptography and recorded in a public dispersed ledger called a blockchain. Bitcoin is unique in that there are a finite number of them: 21 million.

BTC is the ticker symbol for Bitcoin on various exchanges. For example, on Coinbase, one of the most popular exchanges, BTC is the abbreviation for Bitcoin.