Final answer:
A warm front forms when warm air replaces cold air, while an occluded front forms when a cold front catches up to a warm front, lifting the warm air off the ground.
Step-by-step explanation:
A warm front forms when a warm air mass moves into an area and replaces a cooler air mass. The warm air is less dense than the cold air and rises over it. As the warm air rises, it cools and condenses, forming clouds and precipitation. On the other hand, a occluded front forms when a cold front catches up to a warm front, cutting off the warm air from the surface. This results in the warm air being lifted off the ground and forming a separate zone of precipitation.
For example, imagine a warm air mass moving towards a cold air mass. The warm air rises over the cold air, forming a warm front. However, as the warm air continues to move forward, it eventually catches up to a cold front. The cold air wedges itself between the warm air at the surface and the warm air aloft, creating an occlusion. This causes the warm air at the surface to be lifted off the ground, resulting in an occluded front.