I've never heard of markdown before. I heard only after registering on STEEMIT.

Some I use a lot like bold, italic, or strikethrough

Using Markdown, you can, for example, type formulas:
such as H₂O, or S = πR ²

How can I explain how to type these formulas? If Markdown does not allow me to do this, then it immediately turns my explanation into formulas.

To prevent Markdown from being clever and allow you to type the text as it is, for this there are such special characters, ``` at the beginning of the section that should be displayed as it is and at the end

H <sub>2</sub> O, will give H₂O, and
S = πR <sup>2</sup>will give S = πR²

You can also create tables using Markdown

Typing text

| Column 1 | Column 2 | Column 3 |
| -------- | -------- | -------- |
| Text | Text | Text |

We will get such a table

Column 1	Column 2	Column 3
Text	Text	Text

But I'd rather describe here those that I almost never used.

When designing headings, I never put them in the center (I did not know about this possibility yet)

Headline at center

# <center> Headline at center </center>

Previously, if I wanted to make text in two columns, I used a table.

<div class = "pull-right">
Previously, if I wanted to do this, I used the table.  
</div>
And now you can do it like this - just text in two columns.

You can place the picture on the left and the text on the right.






... or vice versa, the text on the left is the picture on the right



I figured out how to place a small image as a link so that when clicked, it opens its large version.

<center><a href="https://big_picture_url.jpg)"><img src="https://small_picture_url.JPG"></a></center>

Now I can change the size of the picture arbitrarily

https://steemitimages.com/100x0/https://steemitimages.com/640x0/https://i.imgur.com/wwK9X46.jpg
https://steemitimages.com/150x0/https://steemitimages.com/640x0/https://i.imgur.com/wwK9X46.jpg
https://steemitimages.com/200x0/https://steemitimages.com/640x0/https://i.imgur.com/wwK9X46.jpg
https://steemitimages.com/250x0/https://steemitimages.com/640x0/https://i.imgur.com/wwK9X46.jpg

My Achievement 1, Achievement 2, Achievement 3
I have been waiting for the verification of achievement3 for a very long time((