What you need to know
A meta description is a short summary that may be used in a search result. Search engines can rewrite it, but a useful description still helps when it is shown and keeps social previews more consistent.
How to apply it
Describe the page's main answer, include a natural topic phrase, and name the specific value a reader will get. Give each important page its own summary.
Common mistake to avoid
Do not repeat the title or write a list of keywords. The description should read like a helpful invitation, not a ranking trick.