An Altcoin is a name given to all the other cryptocurrencies that are based on the Bitcoin protocol. They are attempts to improve (or scam) upon Bitcoin by tweaking parameters such as confirmation time, total coin supply, and mining algorithm. There are hundreds of them.
The term “altcoin” was created by the combing of the words alt, or alternative, and coin, signifying a cryptocurrency. By combining the two words it suggests that the cryptocurrency is an alternative to Bitcoin. There have been many projects that have attempted to imitate the success that Bitcoin has had, which is why projects may try to associate themselves to Bitcoin.
In general the altcoins were built on the same framework as Bitcoin, but with improved features such as faster or cheaper transactions, or a better mining process. Though many features of altcoins can overlap, they also have wide variations in comparison with one another.
While there are now over a thousand altcoins in competition with Bitcoin, it remains firmly at the top of the heap. The cryptocurrency space is evolving very rapidly though, and modifications that include immediate transfers, privacy, different proofs and many others have been taking the stage. Some examples of the more well-known altcoins includes Dogecoin, Litecoin, Zcash, OKCash, and many, many others.