Good question asked! Let me justify you difference between the Google analytics impression VS clicks. And which is the most important role in Google analytic.
For your first question, it would depend on where you are seeing the impressions metric however in general this means the number of times an ad was shown or your site was shown in SERP’s. The number of time someone searched for a term. Your site will not show up for every search of a related key term.
For second question, a click-through is the actual number of times someone has taken their cursor, placed it on your advertising image and used their mouse to click on that image and be taken to your website. This is the most advantageous way to purchase advertising for the advertiser, because it really takes all the guess work out of the equation. You’ll know exactly how many visitors will visit your site relative to the ad purchase. Once the end-user is on your website, it should be engaging and interactive enough to generate some sort of emotion to make contact with you.
So don’t worry about on that, In Google analytic Clicks are most important factors for your healthy business.