Spaces

1. Single Space  :   
2. 2 Spaces  :   
3. 4 Spaces  :   
4. Tab Spaces  :  4 times  

Bold

Syntax: **<text>** or __<text>__
Example:
**This is a Bold Text**  :  This is a Bold Text
__This is a Bold Text__  :  This is a Bold Text

Italic

Syntax: *<text>* or _<text>_
Example:
*This is a Italic Text*  :  This is a Italic Text
_This is a Italic Text_  :  This is a Italic Text

Strikethrough

Syntax: ~~<text>~~
Example:
~~This is a Strikethrough Text~~  :  ~~This is a Strikethrough Text~~

Bold and nested Italic

Syntax: **<text>** and __<text>__
Example:
**This text is _extremely_ important**  :  *This text is extremely important*

All bold and italic

Syntax: ***<text>***
Example:
***All this text is important***  :  All this text is important

Subscript

Syntax: <sub><text></sub>
Example:
This is a <sub>subscript</sub> text  :  This is a _subscript text

Superscript

Syntax: <sup><text></sup>
Example:
This is a <sup>superscript</sub> text  :  This is a ^superscript text

Horizontal Rule

Syntax: --- or *** or ___

Underline

Syntax: <ins><text></ins>