It's a fast and secure way of interacting with the Ethereum blockchain. This Ethereum client powers much of the infrastructure of the public Ethereum network and is used by companies and users alike.
Parity comes with an extensive, easy to use, in-built Ethereum Wallet and Dapp environment that can be accessed via your Web browser of choice.
With Parity one can also develop smart contracts and decentralised applications or build protocol extensions.
Parity is designed for mission-critical use in enterprise environments. Parity has a number of features that make it perfect for deployment in private or consortium setting.
Briefly, Parity is an Ethereum client, written from the ground-up for correctness-verifiability, modularisation, low-footprint and high-performance. To this end it utilises the Rust language, a hybrid imperative/OO/functional language with an emphasis on efficiency.