Impression Share is a digital advertising metric that measures the percentage of total impressions your ads receive compared to the total number of impressions they were eligible to receive. It reflects how often your ads are shown relative to the number of times they could have been displayed based on your targeting settings, budget, and bid.
For example, if your impression share is 70%, it means your ads were shown 70% of the times they were eligible to be shown. This metric helps advertisers understand the visibility and reach of their ads and can indicate whether there are opportunities to increase ad exposure by adjusting bids, improving ad quality, or increasing the budget.