Explain the use of the div tag and the span tag in an HTML document. What is the primary difference between these two tags?  How are they similar.

The div and span tags are used in HTML for different purposes.

1. Div Tag: The div tag is a block-level element that is used for larger chunks of code or bigger sections. It is used to group HTML elements together and apply CSS styles to many elements at once. For example, you might use a div tag to section off all of the content in your website's header or to create a container for multiple paragraphs of text and images.

2. Span Tag: The span tag is an inline element used for a small chunk of HTML inside a line, such as a single word or sentence. It is used to apply styles to specific pieces of content within the text. For example, you might use a span tag to change the color of a single word in a paragraph.

The primary difference between these two tags is how they display on the page. Div elements will start on a new line and take up the full width available, creating a "block." Span elements, on the other hand, only take up as much width as necessary and do not force a new line, making them "inline" elements.

Despite their differences, div and span tags are similar in that they both serve as containers for other content and can be used to apply styles to that content. They are both neutral elements, meaning they don't have any inherent styling or behavior, and are used purely for grouping and applying styles.