Scanning and skimming are both reading methods that can be broadly referred to as reading skills defined by speed orientation. However, each of the techniques serves a different purpose.
In scanning one can find a few useful phrases and with quick glances and rapid eye movement tries to finish reading the relevant parts of a document and the whole sentence is understood better for its main idea rather than the individual details.
Example 1: Looking for the term ‘sedimentary’ from the list of definitions or glossary.
Example 2: Looking for the time and the place for a party as reported in the body of the article.
On the other hand skimming is the reading of a written tribute with an aim of finishing it within the shortest time possible. In this case, heading, subheading as well as some sentences are scanned to get the general view instead of the detailed scope.
Example 1: Almost all readers just go through the topics and headings of all the information seek and other periodicals and are mostly interested in reading the high lights of the dailies.
Example 2: Some readers may first flip through a more or less related chapter of a book to examine it before actually reading it.