IOTA is described as 'open-source distributed cryptocurrency focused on providing secure communications and payments between machines on the Internet of Things' and is an website in the Bitcoin & Cryptocurrency category. There are more than 50 alternatives to IOTA, not only websites but also apps for a variety of platforms, including Windows, Linux, Mac and Android. The best alternative is Bitcoin, which is both free and Open Source. Other great sites and apps similar to IOTA are Monero (Free, Open Source), Ethereum (Free, Open Source), Litecoin (Free, Open Source) and NameCoin (Free, Open Source).
Bitcoin is a peer-to-peer digital currency. Peer-to-peer (P2P) means that there is no central authority to issue new money or keep track of transactions. Instead, these tasks are managed collectively by the nodes of the network.
Monero is a digital currency that is secure, private, and untraceable. It is open-source and freely available to all. With Monero, you are your own bank. Only you control and are responsible for your funds, and your accounts and transactions are kept private from prying eyes.