In Hypertext Markup Language (HTML), tags are the building blocks of web pages. They're special keywords enclosed in angle brackets (`<` and `>`), which instruct web browsers how to display content and structure a webpage.

Here's a breakdown:

* Purpose: Tags tell the browser what kind of content is being displayed. For example, a `

` tag signifies a paragraph, a `

` tag indicates a heading, and an `` tag specifies an image.

* Structure: Tags are often used in pairs. The first tag is called the opening tag (``), and the second is the closing tag (``). The content between the opening and closing tags is the content being displayed.

* Attributes: Some tags can have attributes to provide further information. For example, `` uses the "src" attribute to specify the path to the image file.

* Examples:

* `

This is a paragraph.

`: This creates a paragraph with the text "This is a paragraph."

* `

Welcome to my website!

`: This creates a level 1 heading with the text "Welcome to my website!"

* ``: This inserts an image with the source "logo.png" and alternative text "Company Logo".

In summary, tags are the fundamental elements of HTML that define the structure, content, and presentation of web pages.