Tezos (ticker symbol: XTZ) is a decentralized blockchain started by Arthur Breitman and Kathleen Breitman. The Breitmans also founded Dynamic Ledger Solutions (DLS), a company primarily focused on developing the Tezos technology and owns the Tezos intellectual property. The currency was launched in an initial coin offering on July 1, 2017.  
The Tezos blockchain runs on the eponymous currency, Tezos. The blockchain technology has unique features which the Tezos team claim allows for the establishing of a "digital commonwealth" in which stakeholders themselves decide democratically the direction of the network's rules and governance.  Tezos facilitates formal verification, a technique which mathematically proves the correctness of the code governing transactions and boosts the security of the most sensitive or financially weighted smart contracts.  Collectively, the Tezos network maintains the decentralized aspect of blockchains while introducing a mechanism to enable collective decision making. 
Tezos governance decisions are made in the blockchain rather than outside of it and are automatically deployed to the network once consensus is reached. This means that those who hold Tezos tokens have power rather than centralized core developers and miners. Developers are awarded tokens if their proposals are approved within the blockchain's parameters. Tezos tokens not only power smart contracts in the network, but also allow votes on protocol amendments. 
The white paper for Tezos was initially published in 2014.  Tezos has the public support of Tim Draper, who says he will participate in the cryptocurrency's Initial Coin Offering (ICO) and who invested in (DLS) the company that created Tezos. The Tezos initial coin offering launched on July 1, 2017.  The Tezos Foundation which is based in Switzerland is overseeing the crowd sale. 
Tezos was in the midst of a law suit alleging that their token sale, wich raised over $230 million, was the sale of an unregistered security. This law suit was formative for the rest of the cryptocurrency market, since the Securities And Exchange Commission began to more closely follow the markets after this high profile case. 
There were also purported internal struggles between the founders and creators of Tezos.