A term referring to any cryptocurrency other than Bitcoin.
Altcoin is a term used to describe any “alternate” digital coin or token other than Bitcoin.
Since Bitcoin was the very first cryptocurrency, future iterations and new cryptocurrencies are all collectively known as “alts” in the space.
A lot of the current altcoins such as Litecoin and Bitcoin Cash are modified copies of Bitcoin, created by either modifying the Bitcoin code or forking the chain to create a new version of it.
The entire variety of alt coins today can be separated by categories, such as proof-of-work, proof-of-stake, privacy, stablecoins, and utility tokens, each with similarities and differences.