Difference between clicks and impression?

Difference between clicks and impression ?

Simply put Clicks, is a marketing metric that counts the number of times users have clicked on a digital advertisement to reach an online property. Ad Impressions is a count of the total number of times digital advertisements display on someone’s screen within the publisher’s network.

Clicks on expanded images, or any image clicks that navigate the user out of Google Search, are counted as a click. Impression: Impressions are counted when the user sees either the thumbnail or expanded image.