IOTA is a non-blockchain cryptocurrency. Instead it uses technology called the Tangle.
There are no miners in the tangle: instead, everyone must verify two previous transactions in order to make one new one. For this reason, IOTA is the only truly decentralized cryptocurrency, as it does not depend of centralized mining farms.Because there are no miners, there are also no fees! This is the best part about IOTA, because it means that you can send tiny transactions (like a millionth of a cent).
This will be huge in the future, especially in the area of social payment platforms, and making money online. It is also very important for machine-to-machine payments, which the IOTA team is focused on (like a drone renting out your wifi for 3 seconds as it flies overhead).IOTA also stands out from other cryptocurrencies because it is quantum-proof. It uses one-time signatures, which cannot be broken by quantum computers in the future. It also uses ternary instead of binary ([-1, 0, 1] instead of [0,1]).
The IOTA team is also working on a small ASIC chip (called JINN) that will make IOTA proof-of-work much faster, and enable all kinds of tiny devices (like your toaster) to make payments on the IOTA network.One last unique feature of IOTA is 0-value payments. You can send a transaction of value 0 on the network, in order to use the data integrity features of the network. For example, BMW is looking as using this for odometer readings: their cars will publish odometer readings to the Tangle every once in a while, so it will be impossible for someone to “spin back” their odometer when they sell their car. 0-value secure transactions can be used by many many industries for creating decentralized interoperable systems. Because of this, IOTA goes way beyond any other cryptocurrency, and is actually more like a new kind of data transfer protocol. It may become as important and ubiquitous as HTTP in the future.