An "Altcoin" refers to any cryptocurrency that is not Bitcoin. While Bitcoin was the first and remains the most well-known cryptocurrency, many other digital currencies have emerged, each with unique features and purposes. Examples of popular altcoins include Ethereum, which enables smart contracts, and Litecoin, known for faster transaction times. Investors often explore altcoins for potential growth opportunities, as some may offer innovative technology or solutions to existing problems in the blockchain space. However, altcoins can also be more volatile and risky than Bitcoin, so it's essential for investors to conduct thorough research before diving in.