What is the difference between Hadith which is graded as Saheeh and Hadith whose chain is Saheeh?

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions. Giving the ruling of Sahih (sound) about a Hadith is exclusively the job of great scholars of Hadith who have large knowledge regarding all the aspects of Hadith. They know the defects of narrators, chains, etc. Based on their deep research of a Hadith they give the rulings whether it is sound or not. When they say concerning a Hadith that it is sound then it is as they said, because they are reliable in their rulings and also they give the reasons for the particular rulings they issue. When they know any defect in a Hadith though the chain is correct, they abstain from grading the Hadith as Sahih. In this case, they ruled that only the chain is Sahih. For example, sometime the chain may be sound but the text of Hadith may be "Shaz" irregular. In this case, they say chain is correct but the text is "Shaz". Shaz means the Hadith reported by a trust worthy person but goes against the narration of a person more reliable than him. Allah knows best.