Block-level elements are HTML elements that start on a new line and take up the full width available, such as headings (h1-h6), paragraphs (p), lists (ul, ol), and divs. These elements are used to structure the layout of a webpage.
Inline-level elements are HTML elements that do not start on a new line and take up only as much width as necessary. Examples include links (a), images (img), and spans. These elements are used to add content to the block-level elements and to add additional formatting.
For example, consider the following HTML code:
In this example, the h1 and p elements are block-level elements, while the a and span elements are inline-level elements. The link and some text within the p element are inline elements because they are nested within the block-level p element.