Immunoblotting is another term for the Western blotting technique.
After the proteins have been separated by Electrophoresis on an agarose gel, the proteins are transferred to a Nitrocellulose sheet. They are then labelled with primary antibodies, to find specific antigens/proteins we are looking for. Secondary antibodies can then be used, which will bind to the primary antibodies to allow the proteins to be identified. This is because the secondary antibody will have a specific property, such as radioactivity, bioluminescence or changing colour, to allowed it to be viewed under certain conditions (UV lamp or presence of chemical etc.). 
If the antibody labelling is done at the same time as the gel electrophoresis, this is known as two dimensional (2D) electrophoresis.
The term immunoblotting comes from the use of antibodies, hence immuno-.
This technique was termed Western blotting in 1981 by W. Neal Burnette. 
This technique is also called the Protein immunoblot.
- ↑ Western blotting. Kuriena B. T., Scofield, R. Hal. Volume 38, Issue 4, April 2006, Pages 283–293
- ↑ “Western Blotting”: Electrophoretic transfer of proteins from sodium dodecyl sulfate-polyacrylamide gels to unmodified nitrocellulose and radiographic detection with antibody and radioiodinated protein A. Burnette W. Neal. Analytical Biochemistry. Volume 112, Issue 2, April 1981, Pages 195–203