An HTML meta tag located in the <head> of a document used to convey a description of the page’s content in the format:
<meta name="description" content="Your concise and incisive description of the page goes here." >
Meta descriptions are not used by search engines in determining a page’s search rankings but may be displayed in search results. This offers webmasters an opportunity to craft a description which may be more inviting to searchers than the generic description a search engine generates. So it is a good practice to include a concise and inviting description for each page.
Most search engines truncate the description after 160 characters. Therefore it is recommended that descriptions be limited to a maximum of about 155 characters.
Since the content of the description is wrapped in quote marks, the use of a quote mark within a description will result in content after the quote mark being ignored. In general it is a good practice to limit descriptions to alphanumeric characters.