Cold fronts are the fastest moving fronts. It happens when a cold air mass (a large body of air with the same humidly, temperature, and density) and runs into a warm air mass. Since the cold air mass is denser than the warm air mass the warm air mass rises above the cold air mass. As it rises it begins to cool. Then once it cools it turns into water vapor that condenses into cumulus and cumulonimbus clouds. Since they move fast they can cause weather changes. They bring strong winds and serve thunderstorms.
Warm fronts are slower than cold fronts. They happen by a warm air mass rising over a cooler air mass (because it is less dense). Clouds and storms often come with this front. But if the warm air is dry scattered clouds form. If the warm air is wet and humid light rain falls. Since they are slower moving than cold fronts it may be rainy or foggy for a few days.
Sometimes when warm and cold air masses meet they don't have enough force to move each other. In a stationary front the to air masses meet and have a "standoff". Where the two air masses meet water vapor forms and the water vapor condenses into big storm clouds. This can last for several, several days.
An occluded front happens when a warm air mass gets stuck between two cold air masses. The colder air masses sink under the warm air mass pushing it upward. Once this happens the two cold air masses meet up and temperature decreases. The warm air mass cools and water vapor condenses. Weather may turn cloudy, rainy, or snowy