whatever you type between * *(two stars ) will automatically turns into bold.
Example : You write
I *really* mean it.
Turns to
I really mean it.


For sending underlined Text
Whatever you type between _ _(two underscores) will automatically turns into underlined text
Example: You write

I really _mean_ it.
Turns to
I really mean it.


For writing Bold+Underline
Whatever you type between *_ _* will automatically turns into Bold+Underline
Example:

You *_mean_* it?
Turns to
You mean it?