A body cavity is any space, compartiment or potential space inside the body that holds and protect organs.
In this image, we can see a body cavity in light red on the top of the head, where the brain is located, which is the cranial cavity.
Right below, we see a cavity in the same red color and in some way connected to the cranial cavity, but in a long and thin shape. It is the vertebral cavity (or spinal cavity), where the structures within the vertebral column can be find.
All of the cavities shown below those two (cranial cavity and vertebral cavity) are divisions of the thoracic cavity. The divisions shown in the image are:
Below the vertebral cavity, we see a cavity in orange, right in the middle of the chest. It is the superior mediastinum, a division of the thoracic cavity.
On both sides of the superior mediastinum, we see two cavities in purple. They form the pleural cavity (enclosing, amongst other organs, the lungs).
In the middle of the pleural cavity, we see another one in green, right below the superior mediastinum. It is the pericardial cavity within the mediastinum, which main function is to facilitate the free movement of the heart.
Below the pleural cavity and the pericardial cavity within the mediastinum, we see a cavity in dark red. It is the abdominal cavity, which is the place where many organs such as the stomach, the liver and the kidneys are.