A primary source is a first-hand or contemporary account of an event or topic. They are the most direct evidence of a time or event because they were created by people or things that were there at the time or event. These sources have not been modified by interpretation and offer original thought or new information. Primary sources are original materials, regardless of format.
Letters, diaries, minutes, photographs, artifacts, interviews, and sound or video recordings are examples of primary sources created as a time or event is occurring. Oral histories, newspaper or journal articles, and memoirs or autobiographies are examples of primary sources created after the event or time in question but offering first-hand accounts.
Primary sources may be transformed from their original format into a newer one, such as when materials are published or digitized, but the contents are still primary. There are many primary sources available online today, but many more are still available in their original format, in archives, museums, libraries, historical sites, and elsewhere.
The concept of ‘primary’ and ‘secondary’ sources is key to studying and writing history. A ‘source’ is anything that provides information, from a manuscript where words tell you things to clothes that have survived centuries and provide details on fashion and chemistry. As you can imagine, you can't write history without sources as you would be making this up (which is good in historical fiction, but rather problematic when it comes to serious history.) Sources are usually divided into two categories, primary and secondary. These definitions would be different for the sciences and the below apply to the humanities. It's worth learning them, they are vital if you're taking exams.
Primary Sources
A ‘Primary Source’ is a document that was written or an object which was created, in the time period in which you are working. A ‘first hand’ item. A diary can be a primary source if the author experienced the events they recall, while a charter can be a primary source of the act it was created for. Photographs, while beset with problems, can be primary sources. The key thing is they offer a direct insight into what happened because they were created at the time and are fresh and closely related.
Primary sources can include paintings, manuscripts, chancellery rolls, coins, letters and more.
Secondary Sources
A ‘ Secondary Source’ can be defined in two ways: it is anything about a historical event which was created using primary sources, and/or which was one or more stages removed from the time period and the event. A ‘second hand’ item. For instance, school textbooks tell you about a time period, but they are all secondary sources as they were written later, usually by people who weren’t there, and discuss the primary sources they used when being created. Secondary sources frequently quote or reproduce primary sources, such as a book using a photograph. The key point is that the people who made these sources are relying on other testimony rather than their own.
Secondary sources can include history books, articles, websites like this one (other websites might be a primary source to ‘contemporary history’.) Not everything ‘old’ is a primary historical source: plenty of medieval or ancient works are secondary sources based on now lost primary sources, despite being of great age.
Tertiary Sources
Sometimes you will see a third class: the tertiary source. These are items like dictionaries and encyclopedias: history is written using both primary and secondary sources and shrunk down to the basic points. We've written for encyclopedias, and tertiary is not a criticism.
Reliability
One of the primary tools of the historian is the ability to study a range of sources and assess which is reliable, which suffers from bias, or most commonly which suffers from the least bias and can be best used to reconstruct the past. Most history written for school qualifications uses secondary sources because they are effective teaching tools, with primary sources introduced and, at a higher level, as the dominant source. However, you can’t generalize primary and secondary sources as reliable and unreliable.
There is every chance a primary source can suffer from bias, even photographs, which are not safe and must be studied just as much. Equally, a secondary source can be produced by a skilled author and provide the best of our knowledge. It’s important to know what you need to use. As a general rule the more advanced your level of study the more you'll be reading primary sources and making conclusions and deductions based on your insight and empathy, rather than using secondary works. But if you want to learn about a period quickly and efficiently, selecting a good secondary source is actually best.