What are primary and secondary sources? What are their uses?

Primary and secondary are terms used to designate the sources we use to qualify their value to us.  Primary sources are accounts that are what we call firsthand accounts, while secondary sources are more removed from whatever is being recounted.  I will provide some examples, and then we can look at why it is important that we make this particular distinction.
Let us suppose you are writing a report for school on the Civil War era.  Some primary sources you might use are letters from soldiers discussing the battles they are in, the kind of food they are fed, or the fact that they have no boots to fight in.  Or you might use lists that a plantation owner made, lists of slaves owned or of slaves sold.  These are examples of primary sources, writing down facts, thoughts, and feelings firsthand. We have a "voice" for the source, generally one that is recounting events fairly contemporaneously with the writing.  On the other hand, you might consult a few books by historians who have written about the era, or you might consult an encyclopedia.  In either case, these are secondary sources, events and ideas filtered through someone else. The historian who writes that the Civil War was a horror was not there, while the soldier and plantation owner were.
When you are learning about a subject and writing about it, it is always better to rely on primary sources when possible.  Many collections of sources such as soldiers' letters and slave lists are available, sometimes in private collections, but sometimes scanned and in repositories on-line.  There is nothing inherently wrong with secondary sources, but they are not contemporaneous and unfiltered information and ideas. When we rely only on secondary sources, we are relying upon a source who has selected what he or she wishes and who has placed his or her own spin upon the materials.
https://go.fold3.com/civilwar_records