Exclusions (which are currently in a "working draft" spec as I write) are kinda like
float in that they allow inline content to wrap around an element. But not exactly a float. Chen Hui Jing has an excellent explanation:
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An exclusion element is a block-level element which is not a float, and generates an exclusion box. An exclusion element establishes a new block formatting context.
An element becomes an exclusion when its wrap-flow property is computed to something