Open ID is a portable, single digital identity, that users can use across the web. Anyone with an OpenID can sign into any site that wants to accept OpenID, without having to create a new username and password.
With OpenID, internet users do not need to create a brand new identity at every site they visit before being granted access. Instead, if a site chooses to become OpenID-enabled, its visitors need only to have previously registered with an OpenID "Identity Provider", such as myVidoop, myOpenID or any other.
Because OpenID is decentralized, any website can enable OpenID to make itself more convenient for its users, and no one has to depend upon a single point of failure.
OpenID is becoming more and more popular, as larger sites begin to accept and provide OpenIDs.