Altcoins

Altcoins, short for "alternative coins," refer to any cryptocurrency other than Bitcoin. They were introduced after Bitcoin to improve upon perceived limitations, such as transaction speed or functionality. 

Popular examples include Ethereum, Ripple (XRP), and Litecoin. Altcoins serve various purposes, such as powering decentralized applications, offering privacy features, or enabling quicker transactions. Some altcoins introduce unique consensus mechanisms like Proof of Stake (PoS) to enhance efficiency.