Scatter is a desktop software that upgraded from scatter classic (a Google Chrome web browser extension), and it allows users to sign transactions and provide private data without exposing keys and unnecessary information while interacting with web applications and decentralized applications communicating with the EOS & Ethereum blockchain.
Scatter is also used to:
- Authenticate with websites without passwords using asymmetrical encryption, similar to how Facebook login works but without ever touching an external server.
- Sign blockchain transactions without exposing private keys. Scatter receives transactions from web applications and returns only signatures for the transactions.
- Websites can request personal information from a user's Scatter such as an email, first/last name, date of birth, or a location (address, city, state, country, zip code, phone) .
- Web Applications will never be able to get any information about a user without their explicit consent. 
Scatter moved away from its Google Chrome extension to the desktop application, although the extension is still available to support systems like Chromebooks. The app is incompatible when both the Chrome extension and desktop app are enabled; they also have incompatible backup formats. 
By allowing web applications to be able to request personal information such as an email along with a transaction signature users get the benefit of single-click transactions instead of having to be lead through multi-page forms. 
Scatter's RIDL (Reputation and Identity Layer) allows Identities registered with it to become unique across all networks and blockchains, gain and give reputation, and take part in a global effort to elevate the entire web's safety by creating a decentralized blacklist/whitelist of applications in a Sybil resistant manner.