Stablecoins are a category of cryptocurrencies designed to have a stable value, typically pegged to a reserve asset, such as a traditional fiat currency like the US Dollar. The primary purpose of stablecoins is to mitigate the price volatility that is common in cryptocurrencies like Bitcoin and Ethereum.

Key characteristics of stablecoins include:

1. Price Stability: Stablecoins aim to maintain a consistent value, often close to $1 per coin, to make them suitable for everyday transactions and as a store of value.

2. Pegging Mechanism: Most stablecoins use one of three pegging mechanisms: fiat-collateralized (backed by reserves of fiat currency), crypto-collateralized (backed by other cryptocurrencies), or algorithmic (maintaining stability through smart contracts).

3. Transparency: Many stablecoin issuers provide regular audits and reports to prove that they hold sufficient reserves to back the coins in circulation.

4. Fast Transactions: Stablecoins are often used for cross-border transfers and digital payments due to their stability and quick transaction times.

5. Privacy Features: Some stablecoins offer privacy features to protect the identity and transaction history of users.

Common examples of stablecoins include Tether (USDT), USD Coin (USDC), Dai (part of the MakerDAO system), and TrueUSD (TUSD). Each of these stablecoins has its own mechanism for maintaining price stability and its own level of transparency.

Stablecoins have gained popularity because they offer the benefits of cryptocurrencies (fast and borderless transactions) while avoiding the extreme price volatility associated with traditional cryptocurrencies. They are commonly used in the crypto space for trading, as a stable store of value, and for transferring value between exchanges or users.