Altcoins refer to all the cryptocurrencies and coins other than the main bitcoin. After bitcoin, many cryptocurrencies and coins came into the market which got the name altcoins. Altcoins have become popular due to high return they gave to investors in past. Some altcoins such as Litecoin has given good returns since launch. Altcoins are risky as compared to bitcoin. Altcoins is a kind of high risk high return investment. Predicting the future of an altcoin is very tough. However if you analyze the project and team very carefully, you can get rough idea of probability of success of an altcoin.