Asalamu wa alaikum,
In a single statement, Hadiths are primarily used for explanation of Qur'an and Qur'an & Hadith jointly together give us a comprehensive and clear guidelines for our way of life and way of working.
Both Qur'an and Hadith are based on 'Wahi" - the 'Revelation' or what we call Divine Guidance.
This Divine Guidance sent through Rasulullah (saw) consists of two parts:
The Quran, The Divinely Revealed Book; it is the actual Word of Allah (swt), both its language and in the finality and truthfulness of its message.
The Sunnah of Rasulullah (swt) or Ahadith are his sayings, precepts, teachings and actions which explained the Quran and further completed its message.
Rasulullah (saw) not only received the Quran, he was also its most authentic interpreter and teacher. He received from Allah (swt) both the words of the Message as well as their meanings.
The Quran explains: It is then We Who must explain It (The Quran) and make it clear.” (Al-Qiyamah 75:19)
The role of Rasulullah (saw) was to explain its meanings to others:
“We revealed to you the Reminder (The Quran), so you may explain to humankind what was sent to them, so that they may mediate and reflect upon it.” (An-Nahl 16:44)
“Just as when We sent a Messenger to you from among yourself to recite to you Our Signs, purify your lives, and teach you the Book and al-Hikmah (the Wisdom) and to teach you what you did not know.” (Al-Baqarah 2:151)
The Quran is very closely associated with the life and teachings of Rasulullah (saw). He was as the best and highest example for us to follow. The Quran says: “You have indeed a good example in Allah’s Messenger.” (Al-Ahzab 33:21)
His life and teachings are Divinely Inspired as mentioned in Qur'an: “He does not speak from some whim, it is merely inspiration that is revealed (to him).” (An-Najm 53:3-4)
And Allah knows the best