Cryptocurrency has various digital currencies like altcoin,litecoin,cardano,bitcoin,ethereum.e.t.c
altcoin is not any specific coin. all coins other than btc are called altcoins. You can convert all coins into two category Bitcoin and altcoins.
My favorite crypto is bitcoin..many economists across the globe have predicted that bitcoin will keep increasing it's value in the coming years
I think 99% crypto investors will like Bitcoin because it is highly trustable and holding by most of the wallet. demand is very high and give you real decentralization. price will increase as many countries,institute,traders are looking to accumulate more btc. price is still low from ATH and we can expect to break ATH in three years