Most cryptoassets are known for one thing above all else: volatility. A stablecoin is a deliberate exception — a cryptoasset engineered to hold a steady value, almost always pegged to a traditional currency like the US dollar, so that one unit is intended to always be worth close to one dollar.
Stablecoins exist to solve a practical problem. Cryptoasset prices can move sharply within hours, which makes them awkward for everyday use as a medium of exchange, or as a stable place to park funds between trades. A stablecoin lets people move value around crypto markets, or send money across borders, without constantly converting back to traditional currency and without the price risk of holding a volatile asset.
Not all stablecoins maintain their peg the same way, and the difference matters. Fiat-backed stablecoins hold reserves of cash and cash-equivalent assets, roughly equal to the number of coins in circulation. Crypto-backed stablecoins are collateralised by other cryptoassets, usually over-collateralised to absorb price swings. Algorithmic stablecoins try to maintain their peg through code and market incentives rather than holding reserves directly — a model that has proven considerably more fragile in practice, with several algorithmic stablecoins losing their peg entirely in the past.
"Stable" describes the design goal, not a guarantee. Before relying on any specific stablecoin, it's worth understanding how it's actually backed, who holds the reserves (if any), and how that backing is verified — the same due-diligence habit that applies to any other cryptoasset.