A pressure balanced shower valve is designed to maintain the temperature of the water when you take a shower. Depending on the age of your home, and the amount of people living in it, you may have experienced a fluctuation in temperature when you take a shower. This usually occurs when someone flushes the toilet or uses another bathroom to take a shower at the same time. A pressure balanced shower valve is a sophisticated device that regulates the hot and cold water that runs out of different taps from your shower. Essentially, it makes sure that the mix of hot and cold water is always the same, no matter what water pressure is coming out of the hot or cold faucet.
While it is funny to watch movies and see someone jump out of the shower when the toilet is flushed because of the scalding or freezing water, it isn't quite the same in real life. Being scalded or frozen isn't so great when it's early in the morning and you are doing something like getting ready for work. This situation is especially more likely to happen if you live in an older condo building or older house.
This is why a pressure balanced shower valve is so important to have in your home. It guarantees that when someone else uses the water in the house at the same time you're using the shower, the temperature does not change. Households with multiple bathrooms and multiple people who use them, either need a little bit of coordination when it comes to using the plumbing, or they can just install the right plumbing equipment (i.e. a pressure balanced shower valve) and everyone can get on with their day just a little bit faster.