Petroglyphs (also called rock engravings) are pictogram and logogram images created by removing part of a rock surface by incising, picking, carving, and abrading. Outside North America, scholars often use terms such as "carving", "engraving", or other descriptions of the technique to refer to such images. Petroglyphs are found world-wide, and are often associated with prehistoric peoples. The word comes from the Greek words petro-, theme of the word "petra" meaning "stone", and glyphein meaning "to carve", and was originally coined in French as pétroglyphe.
The term petroglyph should not be confused with petrograph, which is an image drawn or painted on a rock face. Both types of image belong to the wider and more general category of rock art or parietal art. Petroforms, or patterns and shapes made by many large rocks and boulders over the ground, are also quite different. Inukshuks are also unique, and found only in the Arctic (except for reproductions and imitations built in more southerly latitudes).
More information on the Wikipedia page 
Petroforms, also known as boulder outlines or boulder mosaics, are human-made shapes and patterns made by lining up large rocks on the open ground, often on quite level areas. More information on the Wikipedia page .
An article on petroglyphs here .