Meta tag description is one of the factors that influence the page description in search engine results (snippet). Meta tag description and the page contents form the snippet.
That's why it must be filled in for each page of the site. Descriptions should be unique and no more than 160 characters. In the description, write the keyword that corresponds to the page topic. But the most important thing is to make the description attractive to the user to convince them to open your site.
You can fill in the meta tag description in the page settings: