Key to Element Types: Display
Block: A block-level element is one that creates a block box by default. All subsequent elements will appear on the next line.
Inline: An inline element is one that creates a line box and doesn't break the line.
Structural: This is an element that is used for document structure or that structures other elements within a specific portion of a document, such as Table, Head, and so on.
Note that an element's display type can be altered using the display property in CSS. The terminology used here is meant to describe the primary default behavior of the element. Some elements can have multiple display types, such as structural and block. Here the primary display type is noted.