Natural history is the research and study of organisms including plants or animals in their environment, leaning more towards observational than experimental methods of study.
It encompasses scientific research but is not limited to it, with articles nowadays more often published in science magazines than in academic journals. Grouped among the natural sciences, natural history is the systematic study of any category of natural objects or organisms. That is a very broad designation in a world filled with many narrowly focused disciplines.
So while natural history dates historically from studies in the ancient Greco-Roman world and the mediaeval Arabic world, through to European Renaissance naturalists working in near isolation, today’s field is more of a cross discipline umbrella of many specialty sciences. For example, geobiology has a strong multi-disciplinary nature combining scientists and scientific knowledge of many specialty sciences.
A person who studies natural history is known as a naturalist or natural historian.
(copy taken from wikipedia – http://en.wikipedia.org/wiki/Natural_history)