Solana is a public blockchain platform. It achieves consensus using proof of stake and proof of history. Its internal cryptocurrency is SOL. Bloomberg considers Solana to be "a potential long-term rival for Ethereum". Like Ethereum, Solana can interact with smart contracts.
Solana's first official testnet was on June 15th, 2018. According to its developer Anatoly Yakovenko, on July 17th the Solana test network achieved 710 sol/s (the peak speed of solana's initial coin offering) at 2990 Nodes (the highest number it has ever had). This testnet also included 10 sharding chains and 38 shards. For more information about Solana's latest developments, see the solana blog.
Solana has a sharded blockchain which it calls "Lattice". Each node keeps track of its own copy of the blockchain and what other nodes it is connected to. It also calculates each node's network weight: how many solanas this node owns and how much time this node has been alive. This calculation is done using proof of history, which is very fast. Lattice can be visualized as a grid where two nodes that are geographically close to each other will form a block together every 5 seconds (this number decreases as solana grows bigger). Because solana uses proof of stake, consensus on solana does not require every single voter to sign onto the same version of history.
The solana whitepaper states that, "Solana uses a custom Proof of Stake protocol to ensure security and fairness at scale. In our model, each block is created by a randomly selected committee of 25 nodes." It also details the solana consensus algorithm as follows: "In this model, validators publish blocks containing signatures of previous messages from other validators in their row and column (multidimensional cube). Each row and column is assigned a weight (number of solanas deposited) and time (optional timestamp). A node can only sign its own row or column; this prevents withholding attacks where one group publishes one version of history and another group tries to replace it with something else."
How Proof of History Saves Energy and Efficientcy
Solana's proof of history is faster and more energy efficient than proof of work (when solana grows to a certain size, solana will use proof of stake instead). Solana's proof of stake protocol has been designed so that solanas are evenly distributed. The whitepaper explains: "To ensure solanas are evenly distributed at the beginning, we require validators deposit solanas before they can participate in consensus". Solana also contains sharding chains, which allow for parallel transaction validation to increase Solana's transaction throughput. "Each shard operates asynchronously to all other shards and maintains its own copy of state and UTXO set."
The developer team behind Solana includes Zane Witherspoon, a former software engineer at Google and Dropbox, and Anatoly Yakovenko, a former software engineer at Qualcomm. Solana's advisor team includes Greg Fitzgerald, who was a core contributor to both Urchin and Urbit.
For Solana's latest updates, see its blog. For solana's whitepaper, see here. In March 2018 solana announced that it had raised $40 million from venture capitalists such as Foundation Capital and Andreessen Horowitz.. Since then it has raised more money from other investors including Khosla Ventures, Multicoin Capital, Combinator, Aragon, and many more.