1. Block-level element: refers to the ability to exist independently. Generally, block-level elements are separated by line breaks (such as starting a new line after the end of a paragraph). Commonly used block-level elements include: p, h1~h6, div, ul, etc. ;
2. Inline element: refers to the existence of other block-level elements, which are displayed immediately between the connected elements without wrapping. Commonly used inline elements include: img, span, li, br, etc.;
3. Top-level element: includes html, body, frameset, behaves like Block-level element, and is an advanced block-level element.