Meta Description
A meta description is the short summary tag in a page's HTML that a search engine may display beneath its result; it is not a direct ranking factor, but a clear, relevant description can improve click-through rate, and Google often rewrites it to better match the searcher's query.
You set a meta description with a tag in the page head, and the typical visible length runs to roughly 150 to 160 characters before it is truncated. The goal is not to stuff keywords but to write an honest, specific summary that tells a searcher what the page delivers and why it answers their query. A description that reads like ad copy for the exact thing the person searched tends to earn more clicks than one padded with terms.
The honest nuance is that you do not fully control what appears. Google frequently rewrites or replaces the meta description with a snippet pulled from the page body when it judges that to be a better match for a specific query, so the same page can show different descriptions for different searches. Treat the tag as a strong suggestion rather than a guarantee, and make sure the on-page copy it might draw from is just as clear.
Because it influences clicks rather than rank, the meta description sits next to the title tag as part of how a result presents itself in the listing. Write it per page, avoid duplicates across the site, and lead with the answer so the value is visible before any truncation cuts it off.