Archives are collections of primary and secondary sources held and maintained by various institutions for their current and potential value for researchers. Digital archives are collections of either scanned hard copies or materials that are "born digital" (produced and published in digital format). Archives can contain documents (such as newspapers, letters, journals, advertisements, etc.), objects, photographs, videos, and other types of materials. In general, archives contain material that is not accessible in other ways, meaning that the items they contain are unique, rare, or otherwise special.
The collections might be thematic (like an archive of women's suffrage materials), regional (specific to a geographical area), organization-based (such as the records of a company or institution), or person-based (the correspondence and documents of an individual).
Archival search requires time an patience to sift through the materials as you as the researcher are often the one crafting a story or making sense of the materials unlike scholarly research where arguments are being presented.
A video tutorial for searching these collections from Dr. Ashleigh Hardin can be found here.