The word Ghargharah means the stage when soul is about to leave the body and reaches the throat. In other words, the time when one suffers the agony of death.
Hadith Hasan means that Hadith the authenticity of which is connected without any technical defect. Their narrators, however, are next to those of Hadith Sahih. In the opinion of Muhaddithin (Hadith scholars), Hadith Hasan is also reliable as Hadith Sahih.