All cryptocurrencies utilize same idea of public bookkeeping (also called blockchain). However different blockchains utilizes different algorithms of consensus (mechanism of achieving transaction validation). Also many blockchains implement different features (Ethereum virtual machine in ethereum for example, scrypt mining algorithm in Litecoin etc.). They all serve similar but slightly different purposes (Bitcoin is good for storing value, LiteCoin offers faster transactions, ETH is good for smart contracts, Zcash gives better anonimity of transactions).