The Kaddish is a Jewish prayer full of praise that is recited during Jewish prayer services and associated with death and mourning.
While to many Jews, the Kaddish is known primarily as the prayer recited at funerals, that wasn’t always the case. Back in the day, after a rabbinic lecture, the rabbinic would freestyle some words in Aramaic. These words would later become standard and recited after any teaching of Torah. In the 7th century, it became standard to teach Torah at every person’s funeral and when you teach Torah you say the words of Kaddish afterwards.
The Kaddish is full of praise. It might sound strange to have this sort of prayer recited during a funeral, but its a way for mourners to get into a space of praise even in their grief. It’s a way to honor the life of the deceased.
The Kaddish also requires a group of Jews in order to recite it because when we’re mourning, we should be in community.