A jungle is a densely overgrown area while a rain forest is a densely overgrown area with overhead canopies formed by tall trees that prevent light from entering. A rain forest is a type of jungle.
Since rain forests have canopies that limit the amount of light, there are relatively few plants on the forest floor. If the rain forest canopy is destroyed, more light reaches the forest floor, causing increased plant growth. Some plants that grow include vines, shrubs and other plants that require significant light to grow. The increased plant growth causes the rain forest to turn into a jungle.