Inline (or text-level) elements define the "small" structure of a Web page. After you've established the 'big' structure of your document with block elements, concentrate on the inline elements. (You might wish to review the difference between the two.)
A classic example of an inline element is this span of bold text. Notice that the flow of text is not interrupted by the bold element. The change of format does not break the line of text.
These are the inline elements covered in this tutorial: