The meta description is an HTML tag, which looks like this in the HTML. Meta descriptions are commonly used on search engine result pages (SERPs) to display preview snippets for a given page. Refer the below image of meta tags reflecting on Google SERP.
Characteristics of a good meta description
- It should be around 135 to 160 characters.
- It should be actionable, in an active voice.
- It should include a call-to-action.
- It could contain structured content.
- It should match the content.
- It should contain the focus keyword.
- The meta description should be unique.
Refer Yoast for more.
Isak