Altcoins, short for "alternative coins," are all cryptocurrencies other than Bitcoin. They were created to improve upon or offer different features than Bitcoin, such as faster transactions, lower fees, or new use cases. Popular altcoins include Ethereum (smart contracts), Solana (high-speed transactions), and Cardano (sustainability-focused). Some altcoins support decentralized finance (DeFi), gaming, or NFTs. While altcoins offer innovation and potential for high returns, they are also riskier and more volatile than Bitcoin. Investors should research each project’s purpose, team, and community before investing. Altcoins play a crucial role in expanding and diversifying the crypto ecosystem.