Fronts are a boundary between two or more air masses. There are four basic kinds of fronts. One, warm front fronts, two, cold fronts, three, stationary fronts, and lastly, occlusion fronts. These types of fronts can bring a variety of different types of weather patterns depending on which air mass dominates the other. 

Fronts can be associated with lift in the atmosphere which are required for cloud formation, active weather patterns, and precipitation. 

The interaction between two or more air masses can affect the structure of clouds. For example, warm fronts often bring a system of stratiform like clouds while cold fronts on the other hand bring narrow bands of clouds, including cumulonimbus clouds, which are responsible for producing thunderstorms, rain/hail, lightning, and tornadoes.