Original article can be found here (source): Artificial Intelligence on Medium
Command mode versus edit mode
In order to understand how to use keyboard shortcuts in Jupyter, it is important to understand the command mode and edit mode.
Edit mode is when you are editing one of the cells within the notebook and all the text you type is entered in the cell you are currently editing (either code or markdown).
Command mode, on the other hand, is the opposite of the edit mode. It is a mode when we are not editing any cell within the notebook, so you are not writing any code or editing text. This is the time when one of the cells is highlighted and the keyboard shortcuts can be used. Al the shortcuts you will use will refer to the highlighted cell.