Primary sources are created during the time the event took place, or created later by those who have directly witnessed what they are describing, and bring us as close to the original event or thought as possible without being filtered, influenced or analyzed through interpretation.
Secondary sources analyze or interpret a primary resource and are produced AFTER an event.
Secondary sources summarize, evaluate, and analytically interpret primary material, often by offering a personal perspective. Use secondary sources to see what others have discussed. They can be a good place to gather background information on a topic. You can also use secondary sources to explore what subtopics have already been explored on a given topic.