This is mostly for my note and remembering. Markdown is very common now, and the simple formatting language trick is very common in other formatting also at least partially. Some sample use cases: GitHub readme, Wikipedia ..
Say you have a file which you want to refer with link [linkname](file.txt) will link to file.txt in current directory with link name “linkname” for file inside folder use [linkname](folder name/file.txt)
<h3>Attaching an image </h3>
![alt text](image.jpg “image title”)
For image “!” mark is very important otherwise it will just link the file and image will not show.
Use “#” for heading Big heading
## for smaller heading and so on
In both above cases you can link to outside world also and in directories also.
Github link for the sample example link(GitHub)