$BTC the trading pair involving Bitcoin (BTC). It essentially means trading Bitcoin against another asset, such as a stablecoin like Tether (USDT) or a fiat currency like the US Dollar (USD). Commonly used pairs are BTC/USDT and BTC/USD. These pairs indicate the exchange rate between Bitcoin and the respective other asset, with the price representing how many of the quote asset (USDT or USD) are needed to buy one Bitcoin.

In simpler terms: When you see "BTC/USDT" or "BTC/USD", it means you're trading Bitcoin for Tether or US Dollars, respectively. The price of the pair tells you how much of the other currency is required to buy one Bitcoin.

Elaboration:

BTC/USDT:

This pair involves trading Bitcoin against Tether (USDT), a stablecoin pegged to the US Dollar. It's often used to minimize volatility when trading Bitcoin, as USDT's price is relatively stable.

BTC/USD:

This pair involves trading Bitcoin against the US Dollar (USD). It's a common pair for beginners and those who want to trade Bitcoin directly with a stable fiat currency.