Altcoins are alternative cryptocurrencies to bitcoin. Examples of altcoins include ripple, zcash, monero and dash.
Altcoins can differ from Bitcoin in a number of ways. Some have a different economic model or a different coin-distribution method, like altcoins that were given away to all citizens of a country. Others employ different proof-of-work mining algorithms, perhaps to resist specialized mining hardware — or maybe they don’t even rely on proof of work at all. Several altcoins offer a more versatile programming language to build applications on top of, while yet others offer more privacy compared to Bitcoin. And there are also altcoins that serve very specific, non-monetary use cases, like domain name registry or data storage pointers.