On every recently built home, the outlets in areas with hard surface floors (vinyl, tile and concrete) that may be exposed to water have outlets with the test and reset buttons. These are called GFI outlets (Ground Fault Intercept). You probably get annoyed with them because they trip or “pop” occasionally and you have to push the reset to turn the power on again. But there is a good reason for that, your safety.
The purpose of the GFI is to add an extra layer of protection beyond the breaker in the electric box. While a high load will “pop” a breaker (i.e. if you exceed the amp rating by using a bunch of appliances in one outlet), the load required to cause that is higher than a human can tolerate. So if you didn’t have that GFI in the bathroom, and you were using the hair drier while standing in a puddle of water, you would have to tolerate 15 amps before the breaker trips, which would throw you across the room and knock you out at the least. To prevent this the GFI has a lower threshold to trip, so if the same scenario were to happen, the GFI would turn off the power before it harmed you. The GFI allows the outlet the same amperage as the breaker (usually 15 or 20 amps) but has a much lower spike amperage. So you can use a hair drier that is constantly drawing 10 amps, but as soon as that (or you) contacts water, the entire 20 amps are being drawn. This would be bad, but because the GFI “detects” the spike, it shuts off.
Generally, GFI’s are only present in hard surface areas where water may collect. There is typically only one GFI outlet that controls a “string” of outlets in each area. Typically , building code requires one in the garage that controls the garage and outdoor outlets, one or two in the kitchen for all of the kitchen outlets, and one in a bathroom that controls all of the other bathrooms.
So the next time you get annoyed at having to push the reset button on a GFI, not only do you know why you are doing that, but you can rest assured that it probably saved you from something bad happening.