<meta> tags are elements of your HTML code that provide structured meta data and information about the page.
Some of this can be used by search engines, the "description" meta tag for instance will be used to fill the the text snippet in search results. You don't strictly speaking have to fill out a description tag, but it is highly recommended. Having an enticing description will improve your click-through rate, resulting in more conversions!
Note: Search engines limit how long of a text snippet they're willing to present. Google limits this at ~160 characters, or a pixel length of ~940px. Good SEO tools for WordPress (like SEOPress and Rank Math) will let you know if you exceed either.
Example:
<meta name="description" content="Northrook is delivering high-quality Web Design, Marketing, SEO and Hosting services to businesses, charities and beyond." />