Technique, a French word, is loosely defined as "a procedure that is used to accomplish a specific task." Now used as a noun, the word can apply to procedures specific to any profession, trade, or even to the many things that we all do in life.
There is technique employed while cooking, driving, mountain climbing, bowling, and even while raking leaves. But, the French had to get their word from somewhere, and that somewhere happened to be ancient Greece. For, the original Greek word was "technikos" which meant 'to be skilful' and pertained strictly to the world of art.
Now just to clarify, there is a big difference between technique and style where artwork is concerned. Technique is the means by which one arrives at an end; that is, the tools and knowledge that are used during a process. Style is much more personal because it is unique to an individual. In other words, technique can be taught, but style must be discovered.
The work of Leonardo da Vinci (1452-1519), gives us a wonderful example of both technique and style. This old master invented a technique now known as "Sfumato," (Italian, meaning smoky).
Simply put, his technique used a very subtle blending of tone to obscure any sharp edges or lines in a painting. He would paint a base color -- an under painting -- in neutral browns or grays. Next he would apply many transparent glazes in layers on top of the under painting. In doing so he skillfully blended one form into another thereby portraying an amazing realism, especially with his human subjects. In his painting titled, "Mona Lisa," her famous face and smile were achieved by this technique, and it is so perfect that his unique style has left us all in wonderment of just what was so amusing 500 years ago.
On the other hand, Vincent van Gogh (1853-1890) used heavy brush strokes while painting with striking, bold colors. To him the colors had a personal meaning and he used them to express his emotions. Along with the bold colors he would sometimes intentionally warp lines. This contributes to a feeling of motion to his work. These things of course were all a part of his own uninhibited style.
As both impressionistic and expressionistic, his work is now considered as foundational to the modern art movement. Paintings like his, "Bedroom in Arles" and "The Starry Night," which were both painted while he was in a mental hospital, leave one with a definite feeling of his mood and personal view of the world. Although he only sold two paintings during his lifetime, (both to his brother), Vincent van Gogh's paintings are now among the most valuable in the world.
Some of his work, as well as the work of many others, can be viewed on line at either the Yale University Art Gallery web site -- www.artgallery.yale.edu -- or the Museum of Modern Art website -- www.moma.org.