The correct answer to this open question is the following.
Although you did not provide further context or references, we can comment on the following.
The two sources to know about history are primary sources and secondary sources.
Primary sources are the ones based on people who lived the historic event or witnessed the historic event and decided to leave some testimony in the form of a letter, a book, or any type of document. It could have been an interview in a newspaper. It could have been photographs or diaries.
Secondary sources are the ones based on primary sources and could be encyclopedias, or books written by a journalist based on primary historical sources and events.
If you want to learn more about history, we recommend you to go to the site of the National Archives where you can learn about different sources of information.