What is the difference between a Mursal, Marfu', Mawdu', and Da'if Hadith, and which ones are acted upon?

The Hadith scholars established terminologies to differentiate between types of Hadith, among them:

- Al-Marfu‘ (elevated): Everything attributed to the Prophet, peace and blessings be upon him, whether it be a saying, an action, or an approval, regardless of whether it is authentic or weak.

- Al-Mursal (disconnected): That which a Tabi‘i (successor) narrated directly from the Prophet, peace and blessings be upon him, without mentioning the Companion.

- Al-Da‘if (weak): That which falls short of the conditions for an authentic (sahih) or good (hasan) Hadith.

- Al-Mawdu‘ (fabricated): The invented, lied-upon Hadith attributed to the Prophet, peace and blessings be upon him, and it is the worst type of weak Hadith.