Macro means large and nature carries the meaning of existing in nature, the world of matter, not made by humans. To put it simply, nature macro photography is extreme close-up photography of very small subjects on natural livings and things. Which the size of the subject projected on the camera sensor or film negative is life size or greater.
The ratio of the subject size to the actual size is known as the reproduction ratio. A macro lens is a lens that capable of reproduction ratios greater than 1:1.