What is a Meta Description?
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.