Altcoins are different coins. There are Dogecoin, Litecoin, Monero, Darkcoin, Magicoin, MaidSafe and a couple thousands of other coins.
Bitcoins are like Dollar and satoshi is like cents (more or less).
You can see for example Darkcoin like Euro, Monero like Pound and so on.
Each different type of coin needs a different type of wallet (in the same way you can't have Dollars and Euro in the same bank account).
Which altcoin has a future and which doesn't... that's a very big debate, really, and you will have to decide for yourself which to invest into.
Thanks dear for telling. I thought Altcoins are a different crypto currency but yes I am familiar with Dogecoins and I guess even Zippcoins are known as Altcoins. Each with a different value.
Dogecoin's value is decreasing but it has a better future I guess.