Primary sources are information sources that document events in the time/era of the event; they are important because they present historical information from the point of view of those living through it. Likewise, secondary sources synthesize, analyze, and review primary sources. Both primary and secondary sources are necessary in nearly every field of study. The examples below will give you a sense of what types of information you could consult in your research.
Documentable Phenomena: elections, migrations, fads, scientific breakthroughs, disasters, political movements, etc.
Primary Sources (that document phenomena): newspaper articles, diaries, letters, photos, videos, tweets, interviews, etc.
Secondary Sources (that reference primary sources): scholarly humanities articles, encyclopedias, books and documentaries that utilize primary sources, etc.