Native ads are built to match the look and feel of the content around them — a sponsored card in a feed, a recommended article at the bottom of a page — rather than sitting in an obviously separate ad slot like a banner.
What actually makes an ad "native"
A native ad unit inherits the fonts, spacing, and layout conventions of its surrounding content, and is typically labeled "Sponsored" or "Promoted" rather than boxed off with a visible border. A banner, by contrast, is a fixed-size rectangle that looks the same regardless of what site or app it appears in.
Performance compared to banners
Because native ads blend into the content stream, they tend to post meaningfully higher CTR than standard banners, which suffer from banner blindness. The tradeoff is integration effort: native ad units need to be styled per placement, while a banner can be dropped into a fixed slot with almost no design work.
Publishers with a feed-based layout (news apps, social apps, marketplaces) generally see the best return from native; simpler utility apps often stick with banners for the lower implementation cost.