BTC is the first, the most stable, the most known. It will always be the main digital currency. Others are just little players trying to take a part of the cake by loud adverts.
There are many flavors of cryptocurrency I mean there are many kinds of it and it depends on your choice. The most popular is bitcoin and it serves us very well as a truly digital currency. Due to its wide adoption, bitcoin is widely use and with bitcoin I think it is enough. But since there are other options (altcoins), on different purposes like the Ethereum that is good for shares, you can choose what you like.