Different research assignments will require the use of different types of sources. Primary sources include original materials and firsthand accounts, which have not undergone interpretation or change. Examples include reports, letters, diaries, patents, dissertations, articles, manuscripts, documents, eyewitness accounts, interviews, newspapers and transcripts. Secondary sources are secondhand accounts usually about primary sources, but modified, interpreted, selected or rearranged in some way. Examples include journal articles, newspapers, essays, reviews, literary criticisms and books.
Some sources can be either primary, secondary or both, such as many books and articles.
Most likely, you will use a combination of the two.