2 Step verification or Second Sign-In verification is an addtional layer of security that protects your account even if your password gets hacked.This feature is already available for facebook and Gmail accounts .Yahoo has also launched Second Sign-In verification for accounts of selected countries (U.S, Canadian, Indian, Philippines).It is expected to be rolled out for all users by March 2012.
If you enable Second Sign-in verification you have to enter a verification code (sent on your mobile) or Security answer after entering your password.This addtional step is required only if your login from a new computer or mobile.
