What is meant by "It was narrated from the Prophet, peace be upon him, through more than one channel"?

The Hadith scholars and scholars of Athar use the phrase "the intent is the multiplicity of theith narration" to indicate that the Hadith was narrated from the Prophet, peace and blessings be upon him, through multiple طرق (chains of transmission) and isnads (lines of authority). "Fath al-Baqi bi Sharh Alfiyat al-Iraqi" stipulates that it is absolutely impermissible to deem a Hadith weak based solely on the weakness of one chain of transmission, as the Hadith may have other, stronger isnads.