Logical properties provide the ability to control layout through logical direction and dimension mappings, rather than hard-coded physical (top, right, bottom, left) mappings. This change moves us away from the physical properties of a screen, and allows us to make more flexible CSS.
Inline is the dimension parallel to the flow of text (default horizontal)
Block is the dimension perpendicular to the flow of text (default vertical)
An example would be margin-inline-start, this is effectively margin-left when working with LTR writing modes, but for RTL writing modes, would apply margin on the right side of the screen.
https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Logical_Properties
keywords: block axis, inline axis