Fall, winter and spring inclement weather builds up dirt, dust and other stains on deck, patios and driveways. These aspects of your home are important to maintain a clean exterior aesthetic look to keep your overall home looking clean and to maintain its value. It is important to pressure wash these areas of your home to keep everything clean, and to maintain the overall value of look of the neighborhood.
The pressure washer is a great power tool to clean the outside of the house, but it also a tool that you must read the operating instructions as if it used improperly, it can be dangerous to unit itself as well to you and others around you.
It also matters what kind of surface you are trying to clean such as wood, concrete, or bricks. Be careful not to have the pressure washer too close to the surface such as wood, as it can strip and damage the software surfaces.
Here is a good overall video of how a pressure washer works from Ask the Builder.