The Three Kings have journeyed from the East to seek out the Child Jesus in the stable. They bear gifts of gold, frankincense and myrrh. New Testament (Matthew 2: 10-12). On the right Christ is shown on the cross at his Crucifixion.
This is possibly a fragment of a predella; or perhaps a small complete picture. A predella is a long horizontal structure supporting the main panels of an altarpiece commonly decorated with diminutive images of saints or with narratives of their lives.