A Meta description is an attribute within your Meta tags that helps to describe your web page. This snippet of text may appear in the search engine results under your headline. Even though Meta data isn't as important for SEO rankings as it used to be, the Meta description still plays a crucial role in on-page SEO.
You can find the meta description on any web page by right-clicking on the page and selecting "view source" or "view page source" and even by pressing "Control" + "U" on any webpage.
Length of Meta Description:
The length of Meta description has been shortened after the last update in December 2017. Now, Google is coming back to previous limits. So always try to keep it from 120 to 159 characters.
Some tips for Meta description optimization
Short Content: It generally makes sense to use two to three short sentences instead of one long sentence.
Keyword: It is still recommended to use the main keyword of the targeted page in the description. Although this is not a ranking factor, it matches the search term by which Google will automatically highlight this word in the snippet. This attracts even more attention to user.
Call-to-Action: A description should always include a call-to-action that encourages users to click on the result.
Special characters: With the aid of HTML codes, special, non-alphanumeric characters can be inserted into the description, such as hooks, hearts or other symbols. This will also highlight the snippet.
Uniqueness: Every description should be unique, just like the title of a page.