Stellar is an open source, decentralized protocol for digital currency to fiat money transfers which allows cross-border transactions between any pair of currencies. The Stellar protocol is supported by a 501(c)3 nonprofit, the Stellar Development Foundation. Stellar diverges heavily from its predecessor Ripple in that it uses a decentralized and open-source network. This means that Stellar has no specific central authority like the employees of a single bank. Instead, multiple nodes exist that work independently to verify and input transactions in the platform's ledger. 

Stellar has a unique method of reaching a consensus among these nodes known as a Federated Byzantine Agreement (FBA). This means that rather than waiting to verify a transaction until agreement, an entire network of nodes comes into agreement; individual nodes will select other nodes they deem trustworthy who in turn select other nodes they view as reliable, and once a quorum is reached (actually involving multiple quorums--referred to as quorum slices) among these, a transaction will be added to the ledger. 


More information here https://stellar.org/