that video demonstrates working the ratios between multiple strobes in a studio set up. your cameras meter is near useless if you want to approach working your exposure like that. if you have the experience with meters and other such things like zone system then you can get by without a meter but if you want to maintain exact control over exposure while using multiple lights in a studio then meters are still necessary.
the video (as most online instructional videos do) assumes the viewer already understands how meters work. to use a meter to its full effect you really need to understand a couple of different things.
first, all meters measure light and give readings for middle grey (or what is sometimes called 18% grey). middle grey is the 5th zone in a 10 step grey scale which represents 10 equal steps from pure white to pure black. zone 5 (middle grey) is the average between pure white and pure black.
second, there are two types of meters...reflective meters and incident meters. reflective meters measure light bouncing off a subject while incident meters measure light falling on a subject. understanding the differences between how these two types of meters work is critical. reflective metering can be problematic at times because light reacts differently depending upon what subject it is bouncing off of. if you meter a white wall with a reflective meter and shoot it at the suggested settings you will get a grey wall. if you meter a black wall and shoot it at the suggested settings you will again get a grey wall. different subject tones will absorb different amounts of the light falling on it (thus giving us the perception of the wall being white or black) but a meter will always try to measure for middle grey, regardless of what the tone the subject is. incident meters forgo the problem of different tones absorbing light differently by measure the amount of light falling on the subject. measure a white wall with an incident meter and shoot at the suggested settings and you get a white wall. do the same with a black wall and you get a black wall.
additionally, reflective meters have several different ways that they will measure light coming through the lens. you will have to refer to your camera system to see the different modes available to you but they generally fall into the following categories:
evaluative: typically measures the entire scene and averages it out
center weighted: typically measures only a portion of the frame in the center and averages that portion
spot: only measures a small single spot in the center of the scene
each of these methods have their advantages and drawbacks depending on the tones present in the scene and the nature of the light you are trying to shoot in. to use these modes effectively you really need to have a very good understanding of different qualities of light and when a certain type of light combined with certain subjects will fool the meter and give less than ideal results. watching videos online or visiting forums wont provide this knowledge...only lots of shooting in various circumstances will provide the understanding you need.
finally, meters are just a tool to gather information to help you decide what your exposure settings should be. they do not tell you correct exposure. exposure is essentially a creative expression and no camera or meter (or electronic device) is capable of making creative decisions...that can only be done by a person.
learn how your camera's meter works by shooting the heck out of it in different available light scenarios. this will strengthen your understanding of light and will inform you of how to approach different studio lighting setups. once you are in studio, an incident meter will be needed if you wish to maintain complete control over all your lights.