How do inline, block, and inline-block elements differ in CSS?

Block elements in CSS indeed start on a new line and occupy the full width available to them. This means that any block-level element, such as a <div>, <h1>, or <p>, will push subsequent elements down to the next line, providing a clear vertical separation in the layout. This characteristic is essential for structuring content in a predictable manner, allowing developers to build layouts that are easy to read and visually coherent.

The other types of elements have different behaviors. Inline elements, like <span> or <a>, do not break the flow of the document; they only take up as much width as necessary for their content and can sit alongside other inline elements within the same line. Inline-block elements combine aspects of both inline and block elements: they flow inline with text and other inline elements, but they also respect height and width properties like block elements. However, they do not start on a new line, making the choice of the block element's behavior particularly distinct in how it handles spacing and layout.

Thus, recognizing that block elements initiate on a new line and extend to full width is essential in understanding how CSS styling affects the structure and design of web pages.