In Compound microscope image is viewed by simple magnifier. It uses two or more convex lenses. The upper lens is called the eye piece and the lower lens is called the objective. The magnifying power is shown in diameter. A real inverted image is formed when an object is in focus.
In Stereoscopes microscope is designed for low observation. It uses incident light illumination. So it produces three dimensional visualization. It includes two eye pieces and two objectives.It uses reflected illumination rather than transmitted illumination. It is used for the study of the surface of solid specimen.
A compound micro scope uses multiple lenses to process light and magnify the image ultimately passing the light through an eye piece lens into your eye.
Micro scopes can come with either one or two eyepieces. Humans have two eyes and see in 3D through a process called stereo vision. Stereo microscopes are like two microscopes in one, providing magnified images for each eye so as to be able to see a 3d magnified image.
Stereoscopes can also refer to a device for viewing 3d photographs. There used to be a toy called a viewmaster that allowed viewing of 3d pictures. Antique stereo scopes were simply two magnifying lenses held in a frame that allowed your eyes to focus onto a double image photograph (two images side by side taking with a special camera with two lenses) The lenses allowed your eyes to focus onto the photos held about eight inches in front of you. Your brain would merge the two pictures and you would see a three dimensional image.