Other forms: contextualized; contextualizing; contextualizes
When you contextualize something, you provide important and relevant background information to make it easier to understand or explain. In other words, you provide context.
If you're learning about a historical event, your teacher might contextualize it by explaining what else was happening in the world at that time: What circumstances set the stage for that particular event? What were people's mindsets at the time, and why? Wars, for example, don't just happen. There are situations, cultural norms, prior events, and ways of thinking that lead to them. Contextualizing is like adding details to a story to make the whole narrative make sense.