Scanning :  Searching for something specific among many things is called scanning. Scanning is an important technique in reading. Keeping any specific information or words in mind, looking over the entire text to find that information/words is called Scanning.

Examples :

1. To search for a word in a dictionary or index.

2. To know a particular information from a text.

Skimming :  The general meaning of the word skimming is to skim quickly, noticing only the main points. Skimming is sometimes called gist reading. It means gist. In other words, skimming is taking a general idea about a text by glancing at it. Skimming is done to get basic idea about any text.

Examples:

1. To see what is in the news on a website or on a paper.

2. When one reads the text only in order to understand the thesis statement, in one or two lines.