Per-Impression ad is also known as CPM (Cost-Per-Impression). Unlike CPC (Cost-Per-Impression), an advertiser is charged only when his/her advert is viewed regardless if the adverted is clicked.
For instance, you visited a site and you saw flash of an advert. That is impression, it shows that an advertiser has paid an agency who got a publisher to serve the advert on his/her web platform.
Note that the publisher would be paid for his/her services. Also, your ad banner should be designed to attract your audience. Click on this link to learn more https://provehub.com/read/designing-an-ad-that-sells
Online advertising is great and is not stressful. You advert will be directed to your target audience and more people will be aware of your online presence.
An agency like https://adnaira.ng/ is cheaper to start with when you want to start your online advert.