BrightID lets all sorts of applications make sure their users don't have multiple accounts so that everyone has a fair share and a better experience.

It solves the unique identity problem through the creation and analysis of a social graph. BrightID works by creating a social identity network that allows people to prove to applications that they aren’t using multiple accounts. By using a social graph of connections BrightID can prove uniqueness without disclosing a large amount of privacy details as found in all sorts of KYC procedures.

Thus BrightID enables new experimental currencies, voting systems, benefit programs, and all sorts of other projects for which it's essential that no one gets to create multiple accounts. As all users have their own unique BrightID.

To summarize. BrightID is a privacy-first social identity network that allows you to prove to applications that you are accessing them fairly with only one account.

Non-Invasive & Private: BrightID does not record any personally identifying information from your online or offline life.
Accessible: The public good is designed for everyone to be able to participate and receive verifications for the baseline and fair rights of access.
Open: Everything about the public good is open to the public, to use, or to steward.