$BTC Bitcoin (BTC) trading pairs—like BTC/USDT, BTC/EUR, or BTC/ETH—allow you to exchange Bitcoin against fiat currencies, stablecoins, or altcoins, serving as the liquidity backbone of crypto markets. Fiat pairs (e.g., BTC/SEK) enable direct Bitcoin purchases via SEPA/Swish but suffer from low liquidity and wide spreads in smaller markets like Sweden. Stablecoin pairs (BTC/USDT) dominate 70% of volume, offering low slippage during volatility, while altcoin pairs (BTC/SOL) let traders pivot between assets without exiting to fiat. Prioritize BTC pairs for tighter spreads (as low as 0.1%), arbitrage opportunities across exchanges, and insights into market sentiment—since altcoin pairs plummet when BTC dominance rises. Swedes should use BTC/EUR over BTC/SEK for better rates.