BTC (Bitcoin) and sats (short for satoshis) are both units of measurement in the world of Bitcoin, but they represent different denominations within the cryptocurrency.

BTC, or Bitcoin, is the main unit of account and the most commonly used denomination. It represents the whole units of Bitcoin. For example, when you see the price of Bitcoin quoted as $50,000, it means 1 BTC is equivalent to $50,000.

On the other hand, sats (satoshis) are the smallest unit of Bitcoin. They are named after Satoshi Nakamoto, the pseudonymous creator of Bitcoin. Each Bitcoin can be divided into 100 million satoshis (0.00000001 BTC). Sats are used to measure smaller amounts of Bitcoin, particularly in microtransactions and for tracking the value of fractional parts of Bitcoin.

While BTC is used for larger transactions and investment purposes, sats are commonly used to describe the value of smaller amounts of Bitcoin or to measure the price in terms of satoshis. As the price of Bitcoin has risen significantly over time, sats have become a more practical unit for discussing and transacting with smaller amounts of Bitcoin.