What do "impressions" mean in Google Search Console?

An impression is counted each time a page from your site appears in Google’s search results for someone - whether they clicked it or not, and even if it sat far enough down the page that they never scrolled to it:

• Visibility, not visits - an impression measures whether your page showed up, not whether anyone came to it.
• A leading indicator of SEO progress - before a page can earn clicks, it has to start appearing, and rising impressions over a few weeks mean Google is showing your pages for a widening set of queries.
• The warning sign - impressions flat at or near zero across 12 weeks is the clearest sign a page is either not indexed or not ranking for anything at all.

Watch the impressions trend in the Performance report over weeks, not days: rising impressions mean the work is landing, even before the clicks follow.