HTML

1. HTML: Hypertext Markup Language is the standard markup language used to create web pages and define their structure and content.

2. Element: An HTML element represents a specific type of content within an HTML document. It consists of a start tag, content, and an end tag (in most cases).

3. Tag: Tags are used to define HTML elements and are enclosed in angle brackets (< >). They indicate the purpose or meaning of the content they wrap.

4. Attribute: Attributes provide additional information or properties to HTML elements. They are defined within the opening tag and contain a name and a value.

5. Headings: HTML headings define the hierarchy and structure of the text content. They are represented by `<h1>` to `<h6>` tags, where `<h1>` is the highest level and `<h6>` is the lowest level.

6. Paragraph: The `<p>` tag represents a paragraph of text in HTML. It is used to structure and format blocks of textual content.

7. Anchor: An anchor is an HTML element represented by the `<a>` tag. It creates a hyperlink, allowing users to navigate to another page or a specific location within the same page.

8. Image: The `<img>` tag is used to insert images into an HTML document. It requires the `src` attribute to specify the image source (URL or file path).

9. Hyperlink: A hyperlink is a clickable element that allows users to navigate to another page or a specific location within the same page. It is created using the `<a>` tag.

10. List: HTML provides ordered lists (`<ol>`), unordered lists (`<ul>`), and definition lists (`<dl>`) to present information in a structured manner.

11. Table: The `<table>` element is used to create tabular data in HTML. It consists of rows defined with `<tr>` tags and cells within each row defined by `<td>` or `<th>` tags.

12. Form: HTML forms are used to collect user input. They are created using the `<form>` element and contain input fields, buttons, and other interactive elements.

13. Input: Input elements (`<input>`) are used within forms to capture user input, such as text, numbers, checkboxes, radio buttons, or file uploads.

14. CSS: While CSS (Cascading Style Sheets) is not part of HTML, it is closely associated with HTML. CSS is used to define the style and layout of HTML elements, including colors, fonts, spacing, and positioning.

15. Div: The `<div>` element is a generic container used to group and style other HTML elements. It helps with organization and applying CSS styles.

16. Semantic Tags: HTML5 introduced semantic tags like `<header>`, `<footer>`, `<nav>`, `<article>`, and `<section>`. They provide more meaning to the structure and purpose of the content.

17. DOCTYPE: The DOCTYPE declaration (`<!DOCTYPE>`) defines the HTML version being used in the document, which helps browsers interpret and render the content correctly.

18. Metadata: Metadata elements, such as `<title>`, `<meta>`, and `<link>`, provide information about the HTML document, including the title, character encoding, CSS stylesheets, and more.

19. Validation: HTML validation is the process of checking the HTML code for compliance with the HTML standards. Validators can ensure that the markup is well-formed and follows best practices.

20. Responsive Design: Responsive design is an approach to web design that aims to create web pages that adapt and display optimally on different devices and screen sizes.