en_tn_condensed/isa/09/02.md

walked in darkness ... lived in the land of the shadow of death

Isaiah speaks of the people living sinful lives and suffering because of it as if they had been walking in a dark or living in a land of shadow of death.

a great light ... light has shone

Here "light" represents hope and deliverance.

the land of the shadow of death

"the land of deepest darkness"