A snippet is a text excerpt that appears below a page's title in our search results and describes the content of the page.
The main purpose of the SERP Snippet Optimization Tool is to allow webmasters and content publishers to strategically construct page titles and meta description tags that will result in aesthetically-pleasing or eye-catching listings in Google's organic search results. Using this tool, you can optimize the content of your titles and snippets to maximize your click-through rate (CTR) from Google. In other words, you can increase your organic search engine traffic for a specific keyword...even if you can't improve your rankings.
Here is a image that describes about the components of a Google snippets, which will surely help you to understand what is Google snippets...
Hey innovativewebart, Here is a relevant link for you to learn about creation of snippets.. support(dot)google(dot)com/webmasters/bin/answer.py?hl=en&answer=99170 Hope I helped...