Impressions click-through-rate: How often viewers watched a video after seeing a thumbnail. Unique viewers: Estimated number of viewers that watched your content within the selected date range. Views: The number of legitimate views for your channels or videos. Views from impressions: Views that originated from impressions for the selected date ... More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.