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Apparently apple had to update the thumbnail of this video. 

<display-inside>

These keywords specify the element's inner display type, which defines the type of formatting context that lays out its contents (assuming it is a non-replaced element). These keywords are used as values of the display property, and can be used for legacy purposes as a single keyword, or as defined in the Level 3 specification alongside a value from the <display-outside> keywords.
<display-inside> css reference