Banner advertising is not what it used to be. It was the early 90's when websites were just beginning to become the vast resources they are today. Hotwired (now called Wired) added a banner to their homepage that read something like "Have you ever clicked your mouse right here? You will".
Banner ads show up across the web. Sometimes they are in a sidebar, sometimes they show up as a leader board at the top of a site, and other times they flood your screen with popups and unsavoury content (you know what I am talking about.)
Browsers have gotten really good at blocking a lot of banner advertisements in 2021 and the annoying pop-up is a thing of the past (for most people - depending on what kinds of sites you browse.) However, banner ads have evolved into "posts" and "feed ads." All of the time spent learning how to employ high CTR techniques in banner advertising still have a place. Modern banner ads are assembled on the fly with dynamic machine learning choosing the text and images based on mathematical predictions on which combinations will yield the highest CTR.
Google Ads just unveiled the Discovery campaign-type where dynamic ads are assembled for Gmail users, YouTube surfers, and news readers alike. Banner ads generate a lot of impressions. They also bring traffic (usually) which a much higher bounce rate. And more often then not, banner advertising is used for remarketing or to attempt to re-engage a website visitor and bring them back to the conversion funnel.
For the most part, you can think of Banner advertising as the old name for Display Advertising. When you hear terms like "programmatic" or "HTML5" ads this often refers to banner advertising.
For the best result, it's usually best to take your creative message and format it for each platform based on their specific dynamic requirements. That will let your banner ad run with the widest possible distribution and also let the algorithms test combinations for you. Alternatively if you try to keep up and design your ad for each specific placement you will have a hard time getting all the variations in place because there are many.
Display advertising can be very effective. We pair it with other campaign types and focused landing pages to maximize conversions.