Lapis is a opaque blue colored stone. It is a very blue blue, the shade you might think of when someone mentions blue as an unalered primary color. In the past it has been used in pigments. Presently, it is used primarily in jewelry.
From ancient times until the early Renaissance, lapis was used for coloration of extremely precious objects, as it was extremely valuable - generally more expensive than gold. In ancient Egypt, lapis was used for inlay in things like the burial mask of Tutankhamen. There is some evidence that it was used as a pigment in the painting of murals in Egypt, the degree of which is not known because of heavy loss to these murals due to abrasion. In the Middle Ages, in Europe, it was powdered and used as a pigment in frescoes and illuminated manuscripts, because it was the only known blue pigment that did not fade quickly. It is the gorgeous blue that you will see in any illuminated manuscript.
In the past few centuries, more effective, less hazardous blue pigments, like cobalt, have been found, so lapis is generally not used as a pigment. It is still used in some Russian Orthdox religious art, continuing with the tradition of working in the same methods that have been used for centuries. In America and Western Europe, lapis is seen primarily in jewelry, especially in Indian Jewelry.