Can you explain the difference between contextualization and outside evidence in a AP U. S. History DBQ?

Contextualization is written in the introduction before the thesis to explain what led up to the event or time period the prompt is addressing to. It is outside evidence but it's counted as contextualization in the introduction. Outside evidence are present in the body paragraphs and are information that cannot be from the documents provided. It can refer to events that were before the event or after the event.