Altcoins are alternative cryptocurrencies that were launched after Bitcoin's success. They generally project themselves as better replacements for Bitcoin. Bitcoin's emergence as the first peer-to-peer digital currency was paving the way for many to follow.
Altcoins are cryptocurrencies other than Bitcoin. They share characteristics with Bitcoin but are also different from them in other ways. For example, some altcoins use a different consensus mechanism to produce blocks or validate transactions. Or, they distinguish themselves from Bitcoin by providing new or additional capabilities, such as smart contracts or low-price volatility.