Like Holochain and Hashgraph, Solana is a next generation infrastructure blockchain. They claim to be a web-scale blockchain for fast, secure, scalable, decentralized apps and marketplaces. I'm not sure what web-scale is supposed to indicate, but I guess they aim at the high capacity of their blockchain infrastructure. They collected something like 1.7M in March in an ICO earlier this year, which is a remarkable achievement. It was in the news recently because Coinbase users can stake Solana tokens: https://cointelegraph.com/news/coinbase-custody-users-can-now-stake-solana. However, I'm not sure how much is hype and how much is real. I'm not involved in the project and don't hold any Solana at the time.