John Grierson defined documentary as the creative treatment of actuality that aims to document reality such as cultures, events, and people in order to inform, educate, and sometimes entertain audiences. There are several types of documentaries including voiceover narration, observational "fly on the wall" films, reenactments, and interviews. Documentaries utilize techniques such as narration, actual footage, archive material, observations, and interviews to convey their message and purpose.