What is the meaning of "Hadith Hasan" (good Hadith)?

"Hasan" (good) Hadith is divided into: "Hasan li-dhatihi" (good in itself), which is a Hadith whose chain of narration is continuous, with a just narrator of light precision narrating from a similar one, all the way to its end, without any shudhudh (irregularity) or illah (defect). And "Hasan li-ghayrihi" (good due to external factors), which is a weak Hadith whose طرق (chains of narration) are multiple, and the reason for its weakness was not due to the narrator's immorality, lying, or extreme negligence. A weak Hadith is elevated to the level of "Hasan li-ghayrihi" when it is narrated through another chain or more that is equal or stronger, and provided that its weakness is slight. The "Hasan" Hadith, in both its categories, is a proof like the "Sahih" (authentic) Hadith, even if it is inferior to it in strength.