Scanning is reading rapidly in order to find specific facts. Scanning is a reading technique that involvs quickly reading a text to get a general idea of the meaning.
example: 

• Scanning a text on population rates to see if statements about population figures are true or false.
  
• Looking for sports scores in a newspaper .
  
  
  Skimming is a way of reading something quickly to get the main idea without reading every word. When skimming, you can look for headings, subheadings, bullet points, and footnotes to get a sense of the main information.
  Example,
  1. you might skim  article to see if it's worth reading.
  2.Moreover, to quick preview of a book you can skim.