What is meant by the science of al-Jarh wa al-Ta'dil?

The science of Jarh and Ta'dil (discrediting and accrediting) is concerned with the men who transmit Hadith, narrations, and reports. It specializes in examining the conditions for their acceptance and the reasons for their rejection. What fulfills the conditions of authenticity is accepted, and what contains a reason for rejection is rejected. The fruit of this science is the knowledge of the authentic, weak, accepted, and rejected Hadith.