Etching involves scratching lines into a metal plate covered with a waxy ground to expose the bare metal where lines are wanted in the finished piece. Lithography was invented in 1796 as a cheaper method to publish works using a sheet of metal to transfer an image or text onto paper using ink. Offset lithography, which came into use in the 1960s, improved on lithography by transferring the inked image from a plate to a rubber blanket and then to paper, making it much cheaper than previous methods. Digital printing, which emerged in the 1990s, refers to printing directly from a digital image to media and avoids the costs of making printing plates for short runs while allowing on-demand and modified printing.

1. Etching
In traditional pure etching, a metal (usually copper, zinc or steel) plate is covered with a
waxy ground which is resistant to acid The artist then scratches off the ground with a
pointed etching needle]where he or she wants a line to appear in the finished piece, so
exposing the bare metal
Lithographs
Lithography was invented in 1796 by German author and actor Alois Senefelder as a cheap
method of publishing theatrical works. Lithography can be used to print text or artwork
onto paper or other suitable material.
People used to add the design onto a sheet of metal, from this they transferred the image
or text onto paper using ink. This is an effective way of printing but it was expensive.
Offset lithographs
Offset printing is a commonly used printing technique in which the inked image is
transferred (or "offset") from a plate to a rubber blanket, then to the printing surface e.g
paper, cardboard. This method came into use in the 1960s and was better than
lithography and is was much cheaper.
Digital printing
Digital publishing started getting used in the 1990s refers to methods of printing from a
digital-based image directly to a variety of media. It usually refers to professional
printing where small-run jobs from desktop publishing and other digital sources are
printed. Digital printing also has a higher cost per page than more traditional offset
printing methods, but this price is usually offset by avoiding the cost of all the technical
steps required to make printing plates. It also allows for on-demand printing, short
turnaround time, and even a modification of the image used for each impression.