What is meant by the Science of Al-Jarh wa At-Ta‘deel?

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

The science of Al-Jarh wa At-Ta‘deel (Criticism of Hadeeth narrators) studies and evaluates the accreditation of Hadeeths and their narrators to determine if they fulfill the conditions which qualify the narration to be authenticated,  and to find out the reasons behind any possible rejection of their narrations. The chain of narrators which fulfill the conditions of authenticity are acceptable; other chains which include one or more reason to justify their rejection means they are rejected.

Criticism of Hadeeth narrators is a science of significant importance and its outcome is that we are able to rate each Hadeeth as either authentic or weak. The same thing applies to accreditation of the narrators.  

And Allaah Knows best.