A plain-language explanation
Meta Description is a description of the page placed in the HTML code, which can be used by the search engine as a fragment of the result.
Where it helps in practice
A description can encourage a search click, although the engine may show a different passage suited to the query.
The decision before implementation
Write an honest value summary, distinguish similar URLs and avoid promises the page does not fulfil.
How to verify the result
Review duplication, device display, CTR in ranking context and cases where snippets are often rewritten.