USDT, BUSD, and USDC are all stablecoins. Stablecoins are cryptocurrencies that are designed to maintain a stable value, usually by being pegged to a fiat currency such as the US Dollar. 

USDT (Tether) is the largest stablecoin by market cap and is issued by Tether Limited. It is closely tied to the US Dollar and is backed by reserves of fiat currency and other assets.

BUSD (Binance USD) is issued by Binance, one of the largest cryptocurrency exchanges. Similar to USDT, it is pegged to the US Dollar and is backed by fiat currency reserves and other assets.

USDC (USD Coin) is another major stablecoin that is issued by Circle and Coinbase. It is also pegged to the US Dollar and is backed by reserves of fiat currency and other assets.

All three stablecoins are popular options for traders and investors looking for a more stable cryptocurrency option compared to the volatility of other coins such as Bitcoin or Ethereum. They are commonly used for trading, remittances, and other financial applications.