I would like to know the meaning of "At-Tanzil" and I thank you very much.

"Tanzil" is a verbal noun derived from the verb "nazala," meaning to bring something down from a higher to a lower place. When used in reference to the Qur'an, "tanzil" signifies Gabriel's bringing it down from Allah to the Prophet, peace and blessings be upon him, as in the Almighty's saying: "Say, the Holy Spirit has brought it down from your Lord in truth" (Quran 16:102), and His saying: "And indeed, it is the revelation of the Lord of the worlds. The Trustworthy Spirit has brought it down. Upon your heart, that you may be of the warners. In a clear Arabic tongue" (Quran 26:192-195). "Tanzil" may also carry other meanings depending on the context.