Cryptocurrencies is a digital asset designed to work as a medium of exchange. It uses cryptography to secure transactions, control the creation of additional units and to verify the transfer of assets. Cryptocurrencies use decentralized control as opposed to electronic money and central banking systems. The decentralized control of each cryptocurrency works through a blockchain, which is a public transaction database, functioning as a distributed ledger. You have the option to store yours coins in an online wallet, online exchange like (coinbase, coinmama) or hardware wallet.
Bitcoin was the first crypto created in back in 2009. Since then, thousands of other cryptocurrencies have erupted. These are relatively referred to as altcoins, alternative coin. Some cryptos have different purposes which is why we expect to see plenty more join the wave. On the other hand most cryptos serve the same purpose. Either used a token of value or to simply spend. You can invest or trade any crypto just like any other currency, stock, indicies, etc