As the major application I'm using on a daily basis, I guess Bash deserves a separated section to be talked about.
Essentially, Bash is a command-line interface shell (CLI shell), contrary to a graphical user interface (GUI). Alternatively speaking, by typing in commands on Bash, one can manipulate files and settings on the computers without touching your mouse; as for a GUI programme, a mouse is necessary to achieve any goal.
Needless to say, there are several operating systems out there, and every of them constructs utterly different GUI guideline for their platforms, which means different user experience.
For Bash, or any CLI in general, the basic language is exact same across different platforms. Once you learnt it, it's done, lifetime, guaranteed.
Of course not. CLI programme can be considered as a replacement of Finder in OS X or Folder in Windows (with more other utilities). For any type of file other than .txt, we can only edit them through other correct softwares.
But it is elegant, efficient, and consistent.
The stack application.
The one I'm currently using, non-complains.
To create a new directory inside another new directory
mkdir folder_name
To go back to upper directory
cd ..(/../../../..)
To delete the directory which is empty
rmdir folder_name
To delete the directory which is not empty
rm -rf folder_name
To go back to the earlier directory
popd
To create empty fils
touch name.format
To input in the empty txt file
cat > filename
input
input
finish with CRTL-d
To copy a file in the same directory
cp old.txt new.txt
To copy a file in another directory
cp old.txt newplace/
To rename a file/directory
mv oldname newname
To view a file in a popped up window
cat file.txt | less
Q to quit
To view a file
cat file.txt
To run two commands at the same time
cd .. && ls
To change the prompt<sup>4</sup><sup>5</sup>
export PS1=" "
<1> For more (and correct) information, please visit Wikipedia
<2> For the complete list, please visit Wikipedia
<3> For more complete command list, please visit here
<4> For more details, please visit here
<5> In order to permanently change the prompt, see here