Different types of sources can be used to obtain information:

Primary sources provide contemporary accounts of an event, written by someone who experienced or witnessed the event first-hand. Some of these original documents include: diaries, letters, journals, handwritten manuscripts, autobiographies, photographs, film footage, and so on.

Secondary sources are sources that describe, summarize, analyze, evaluate, are derived from, or are based on primary-source materials. They may provide criticism or interpretation of the primary source. Some examples include books, journal articles, biographies, radio or television documentaries, pictures, quotes, and so on.

Secondary sources can be very helpful in supporting your own thoughts or opinions on a topic. For example, if you collect data about voting patterns and make a claim about your findings, you can strengthen your argument by backing it up with an opinion from a secondary source.