Primary sources are the evidence of history, original records or objects created by participants or observers at the time historical events occurred or even well after events, as in memoirs and oral histories. Primary sources may include but are not limited to: letters, manuscripts, diaries, journals, newspapers, maps, speeches, interviews, documents produced by government agencies, photographs, audio or video recordings, born-digital items (e.g. emails), research data, and objects or artifacts (such as works of art or ancient roads, buildings, tools, and weapons). These sources serve as the raw materials historians use to interpret and analyze the past.

-- "Primary Sources on the Web: Finding, Evaluating, Using", American Library Association, January 12, 2015.

http://www.ala.org/rusa/sections/history/resources/primarysources 

These sources analyze and interpret primary sources, typically in order to make some sort of argument. Secondary sources could be published any time after the publication of the primary sources they refer to, from almost immediately after, to hundreds of years later.

ex. Articles or books that interpret original research or creative works, biographies, historical analyses.

Sources that compile information from secondary and primary sources. They tend to be objective and factual.

ex. Encyclopedias, almanacs, bibliographies, and other reference sources.