Offset printing works in a simple manner. It uses three cylinders to transfer the image onto the substrate. 
The first cylinder is mounted with the printing plate. The image on the printing plate is ‘right’ reading or written with the right side up. 
The first cylinder is inked and the image transferred or offset onto the second cylinder, which is mounted with a rubber blanket.
 The image on the second cylinder is thus reversed or becomes ‘wrong’ reading. Finally the image is transferred from the blanket cylinder onto the third cylinder or the substrate. 
The substrate is mounted on the third cylinder also known as the impression cylinder. The image once again is reversed and becomes ‘right’ reading or right side up in the final printed version.
A unique characteristic of offset printing is that the image and non-image areas are on the same surface level. 
The printing method uses the chemical fact that oil and water do not mix to print from a single surface level. 
In fact, offset printing acquired this method from lithography and thus it is often referred to as litho offset printing as well.