These lenses are used as condensing or magnifying lens 

Objectives or magnifiers are made up of the biconvex lens

Imaging systems like microscope, telescope, monocular, binoculars, camera and so on utilizes the biconvex lens in their manufactures.

The biconvex lens is used to produce the virtual image which is used to clear the defects in the human eye and real image in some photographic films and is also used in optical sensors. 

The biconvex lens is used in the burning glass. 

The biconvex lens also plays an important role in image relays and is used in different optical industries.