Divine illumination means that God helps people understand things in a special way. It is like a special light that God shines on our minds so that we can know truths that we couldn't know otherwise. This light helps us to see things clearly and to understand them better. It is not like a flashlight or a lightbulb, but more like a special kind of knowledge that comes into our minds when we ask God for help. So, when people say they are being illuminated by God, it means they are gaining a deep understanding of something important through God's help.