IOTA ($3,25) is one of the most important cryptocurrency, ranked 7 on Coinmarketcap. it's technology is way different than the bitcoin:
The IOTA cryptocurrency was created for the IOT (internet of things) world and it's very interesting because it's more resistant at hack than the blockchain, even an Quantic attack.
I let you with a great video by Cryptonauts which explain all the system perfectly !