To literally 'crack' something means to cause a break in the surface of something without separating the structure, such as a plate, glass, or an egg.
However, as the video shows, 'crack' is very versatile, and can be used in both a social and professional context, though usually only informally. To make it a little easier to understand how and when to use this word, the examples given in the video have been grouped according to their meaning below:
Crack a smile, crack a window - open something slightly. In the case of 'crack a smile,' you open your mouth slightly.
Crack a puzzle, code, case, or cracked it - solve a problem or come to understand something difficult, usually after time and effort.
Crack on, get cracking - continue doing or start to do something with urgency and determination.
Crack up, crack under the pressure - be affected by something to the point that you are unable to function normally or perform to an expected level.