An impression is how often your Text Ad was shown on Google’s Search Engine Results Page, before the user has clicked on your Text Ad.
An Impression is counted each time the Text Ad is shown on the Search Engine Results Page on Google’s Search Network.
Impressions can boost brand awareness by an average of 80%. A strong impression can lead to a sale and a compelling impression can lead to a click.
To find out how many impressions have shown for your Text Ad you can go to the “impressions” column in Google Ads.
Source: Impressions: Definition