When you are skimming through a document, you are very quickly reading through it and noting only the important information. You will not read every sentence in its entirety. For e.g. "I skimmed through the articles in today's paper and we had some interesting news today!" When you are scanning a document, you are quickly reading through it while looking for relevant information. You may then read the relevant information in more detail. For e.g. "I scanned the papers to look for interesting news on the flood."

In scanning, you move your eyes quickly identifying the main ideas of the book/website material , seeking a specific word, phrase, number or idea. Unless you practice scanning, you may waste a lot a time while trying to read reference books/websites.

If you are skimming a book/website/documents, you should read the blurb, the preface and table of contents. The Chapter headings provide a reliable indication of the content of the book. You can turn the pages randomly and check its readability, style and seriousness in terms of treatment. You can focus your attention on subheadings, bold, italicized or underlined text, diagrams, graphs, charts and photographs, if any. If there are chapter summaries, you get the vital points quite easily. You can go to the text to find the details of points in the summary you found interesting. Once you find that the book is worth detailed study, you can go for it.

skimming to read superficially while scanning to read metrically. cowboy...