Block-level content

In CSS, content that participates in block layout is called block-level content.

In a block layout, boxes are laid out one after the other, vertically, beginning at the top of a containing block. Each box’s left outer edge touches the left edge of the containing block. A block-level element always starts on a new line. In horizontal writing modes, like English or Arabic, it occupies the entire horizontal space of its parent element (container) and vertical space equal to the height of its contents, thereby creating a “block”.

Note: The above behavior of block layout changes if the containing block’s writing-mode is set to value other than the default value.