Headings

You can create headings by starting a line with one or more # characters, followed by a space and the heading text. The number of # characters you use will determine the heading level. For example:

# Heading level 1
## Heading level 2
### Heading level 3
#### Heading level 4
##### Heading level 5
###### Heading level 6

Emphasis

You can add emphasis to text by using the * character for italicized text or the ** characters for bold text. For example:

*Italicized text*
**Bold text**

Lists

You can create unordered lists by starting each list item with a * character, followed by a space and the list item text. For example:

* Item 1
* Item 2
* Item 3

You can create ordered lists by starting each list item with a number, followed by a . and a space, followed by the list item text. For example:

1. Item 1
2. Item 2
3. Item 3

Links

You can create a link by enclosing the link text in square brackets, followed by the link destination in parentheses. For example:

[Link text](http://example.com)

Images

You can insert an image by using an exclamation mark, followed by the alt text in square brackets, followed by the image destination in parentheses. For example:

![Alt text](http://example.com/image.jpg)

Code blocks

You can create a code block by enclosing your code in three backticks (“`). For example:

Code goes here

You can also specify the programming language to use syntax highlighting by adding the language name after the first set of backticks. For example:

```python
Code goes here

## Tables

You can create tables by using the `|` character to separate columns and the `-` character to create a header row. For example:

Column 1	Column 2	Column 3
Cell 1	Cell 2	Cell 3
Cell 4	Cell 5	Cell 6

Blockquotes

You can create a blockquote by starting each line with a > character, followed by a space and the quote text. For example:

> This is a blockquote
>
> It can span multiple lines

Horizontal lines

You can create a horizontal line by using three or more -, *, or _ characters on a line by themselves. For example:

---

***

___

Task lists

You can create a task list by starting each list item with a - character and a space, followed by [ ] or [x] to indicate whether the task is complete. For example:

- [x] Task 1
- [ ] Task 2
- [ ] Task 3

Emoji

You can insert emoji into your text by using the colon character followed by the emoji code. For example:

:smile: :heart: :thumbsup:

There are a few additional elements that can be used in markdown, although they are not as commonly used as the ones I covered in my previous response. Here are a few examples:

Definition lists

You can create a definition list by using the : character to define the term and the definition. For example:

Term 1
: Definition 1

Term 2
: Definition 2

Footnotes

You can create footnotes by using the [^footnote] syntax to create the footnote reference, and the [^footnote]: syntax to define the footnote text. For example:

This is some text with a footnote[^footnote].

[^footnote]: This is the footnote text.

Abbreviations

You can create an abbreviation by using the *[abbreviation]: syntax to define the abbreviation and its expansion, and then using the *[abbreviation] syntax to reference the abbreviation in your text. For example:

*[HTML]: HyperText Markup Language
*[CSS]: Cascading Style Sheets

I am familiar with HTML and CSS.

I hope this reference guide helps!