The Quran is the word of God Almighty and Wise and within this Quran He put forth the challenge to all the great poets and people who specialized in literature to come forth and bring something like it. When the literary experts heard this Quran they were amazed and either said that it is the word of God or either that it was magic, but it definitely was not the work of a mortal human being.
God describes the Quran being sent to the people as follows:
كِتَابٌ فُ ِّصلَتْ آ َيا ُتهُ قُرْآنًا َعرَ ِبيًّا لِّ َقوْ ٍم َيعْلَمُونَ
“A Book whose verses have been detailed, an Arabic Qur'an for a people who know.” Quran 41:3
They would make noise so that others would not hear the heavenly words and be persuaded to follow the prophet Muhammad (s).
وَقَالَ الَّذِي َن كَفَرُوا لا َت ْسمَعُوا لِ َهذَا الْ ُقرْآنِ وَالْغَوْا فِيهِ لَعَلَّكُمْ َتغْلِ ُبونَ
“And those who disbelieve say, "Do not listen to this Qur'an and speak noisily during [the recitation of] it that perhaps you will overcome." Quran 41:26
The experts were not able to refute the Quran or produce anything like it so they turned to fighting the holy prophet (s) and his followers. This itself shows the truthfulness of the Holy Quran, because it would have been much easier to just produce one surah like it the amount of Surah Kawthar, which is just 3 ayats, rather than going to battle and losing many lives. We see however that they were not able to challenge the Quran and this was also stated by God that they would not be able to nor would they ever be able to.
The Quran speaks of many scientific things that were unknown to people back in the time of the prophet of Islam. Now days we see that science is confirming and attesting to what was mentioned in the Quran dating back to the year 610 AD. Some of these things that were mentioned in the Quran were the detailed description of the stages of the creation of man in the womb, the planets all in orbit, the mountains are as pegs in the earth meaning that as they go up in the sky they also delve deep into the Earth, the layers of the sky, plants being created in pairs of male and female, the salt water and fresh water seas not mixing with each other, the universe expanding and many more scientific miracles which whole books have been dedicated to.