Altcoin is basically any other cyptocurrency other than Bitcoin. As bitcoin is an open-source project, most of these altcoins are actually a fork from bitcoin itself except for a few with the codes having written from scratch. Altcoins in the past were seen as a perfect opportunity to be used as a test platform for developers to refine and further improve bitcoin features. As this moves along, coins were then created with the ultimate aim and intention of providing a solution to bitcoin problems and to replace it as the leading cryptocurrency.
However, recently scams involving creation of new altcoin have become rampant (most of them projecting promising roadmap with the aim of soliciting funding and investment) which later did not develop into full-scale project, thus have seen people ditching the mentality and to quickly label altcoins as simply “untrustworthy”. However, it is obvious that this stereotyping does not do justice to the rest of the coins.
As of this writing on October 3, 2015, there are