Do you know where your main electrical shutoff is? Most people will never use their main shutoff unless they are working on their electric panel. So why is it important to know?
Your main electrical shutoff is a safety feature. It is there when we need it in an emergency and not just when work is being done. Imagine that there was an electrical short or some other sort of electrical issue in your home and you didn't have your main shutoff. You would have to search through all of your breakers trying to find the right one to turn off the area that you want to turn off. With the main shutoff you can turn all the power off with the main switch.
So where is it located? Your main breaker is generally the largest breaker in your panel all the way at the top. Some panels don't have a single main shutoff, and may have several breakers as a shutoff. While this is acceptable, there should never be more than 6 shutoff switches.