I would love to emphasize on how stable coin, as the name implies, is just as its name sounds, stable. Your currency saved in stable coins will remain same without adding up interest as BTC does because it works as a stable asset one can keep just like other cryptos but they aren't just any other cryptos too.
BTC is volatile as are other crypto currencies, one minute the price is up, the next, it is down. Within the few minutes, one can become a millionaire or simply loose and become broke or bankrupt from trading their crypto.
That's why instead of using a more volatile decentralized asset that isn't a regular bank to save money or make payments which have same value as the local Fiat, stable coins serves just fine.
Some of the top five stable coins one can use remains the Tether (USDT), USD Coin (USDC), Binance USD (BUSD), Dai (DAI), and TrueUSD (TUSD). Others exist, but these are more accepted.