The meta description is an HTML element in the page <head> that briefly summarises the page's content. Google can display it as the description in the search result.
The sits as <meta name="description"> in the page head and is normally invisible to visitors. In the search result it can appear under the title, acting like a small advert that invites the click.
It is not a direct ranking factor, but it influences the . Guidance:
aim for roughly 120 to 160 characters, with no fixed Google limit,
put the key message in the first 100 to 120 characters,
give every important page its own description,
mention the main early and show a concrete benefit.
Google does not always use the supplied description: if a from the page content fits the query better, or the description is too generic or duplicated, Google generates its own snippet. Studies show Google frequently rewrites meta descriptions.