Ok now i get what is alt coin but why is it so better than bicoins?
And how do I mine it?
As chuckbuck said, it isn't much better. However, some alt coins are created to be GPU/ASIC resistant, allowing users to mine on their regular PC while still getting a good amount of coins. Also, there are alt coins who promote anonymity by building mixers into it, eg darkcoin. Or POS, proof of stake and allow users who have coins in their wallet to run it as node to verify transactions and earn coins. There are loads of miner available to mine it, depending on what algorithm is the coin based on.