Meta description tag

An important tag describing the content of the website used by the search engine in the search result snippet. If left empty the search engine will pick a paragraph from your content to display in the snippet.

Google will also ignore your description if it is too long, so it is a good idea to stay under 757px for mobile and 940px for the desktop.

It does not necessarily influence your SEO but taking control of what is displayed in the search result snippet can greatly improve your click-through rate.