The main use of this phrasal verb is to express a mechanical or technical failure, such as that of a vehicle, or to say that something or somebody is not functioning normally.
If a car breaks down, it literally stops working. In a figurative sense, that meaning can also be used to refer to the failure of a plan, relationship, negotiation, or even the human body. If that has stopped functioning as it should, or is in bad condition, you can say that it has 'broken down.'
The same can be said if your mind is badly affected by something negative, like stress or sadness. In that case you can also say that you have 'had a breakdown,' or are on the verge of one. Similarly, to 'break down in tears' is to be overcome by them so that you temporarily cease to function as you normally would.
This phrasal verb can also be used in reference to separating something into different or smaller parts. You can 'break down' something by explaining it step-by-step, analyzing it, or arranging it into different categories. Similarly, if the structure of something separates or decomposes, you can say that it 'breaks down.'
As the video shows, this phrasal verb can be used in a professional context, but is more common in a social one.