Altcoins, short for "alternative coins," are all cryptocurrencies other than Bitcoin. Since Bitcoin was the first cryptocurrency, altcoins emerged as alternatives offering different features, technologies, and use cases. Altcoins are diverse in nature, ranging from coins designed for specific applications to those focusing on privacy, smart contracts, and decentralized finance (DeFi). Some of the most popular and established altcoins include Ethereum (ETH), Litecoin (LTC), and Ripple (XRP).

Altcoins generally aim to solve problems or introduce new functionalities that Bitcoin doesn’t address. For instance, Ethereum's blockchain allows developers to create decentralized applications (dApps) and smart contracts, which are self-executing contracts with the terms directly written into code. Similarly, privacy coins like Monero (XMR) and Zcash (ZEC) are designed to offer enhanced privacy features, allowing users to transact anonymously.

The value of an altcoin is often determined by its technological innovation, market demand, and use case. Most altcoins have a clear purpose or utility, which can help support their price in the long term. Investors tend to focus on the practical aspects of these coins, such as their potential to disrupt industries, solve problems, or provide improvements over Bitcoin's framework.