Here's a breakdown:

* Air masses: Large bodies of air with relatively uniform temperature and humidity.

* Fronts: Boundaries between two different air masses.

There are four main types of fronts:

* Cold front: A cold air mass pushes into a warmer air mass, causing rapid lifting, thunderstorms, and sometimes severe weather.

* Warm front: A warm air mass slides over a colder air mass, creating a gradual rise in temperature, light rain, and possibly fog.

* Stationary front: Two air masses meet but neither has enough force to displace the other, leading to prolonged periods of rain or snow.

* Occluded front: A cold front overtakes a warm front, lifting the warm air mass off the ground. This can lead to complex weather patterns, including heavy precipitation and thunderstorms.

The interaction of these fronts is a key driver of weather patterns around the world.