A short description of what the particular web page is about. This will be displayed on the SERPs under the website title. While these aren’t necessary, they do give the searcher a good idea of what can be found on the site. If a meta description is omitted, Google will automatically fill up the space under the title with the first sentences of copy (or a portion of the copy containing the searched keywords) on the page. The disadvantage of this is that there is only so much text that can fit in the area, so a sentence may end up truncated by Google. Including a meta description gives the webmaster control of exactly what the searcher will see on the SERPs.