Rain forests in the tropics receive a lot of sunlight which is converted into vast amounts of plant food by the process know as photsynthesis.The vegetation is therefore very lush, and this provides food for many different types of animals too.
A rainforest offers several different types of environments for plants and animals to flourish. There is usually some sort of water source for amphibians to live in. There's also the ground area, the trees themselves, and the upper canopy. The canopy of the rainforest by itself provides lots of places for plants to grow and animals to live.
As regards the plants, you have the ones on the forest floor that don't grow very tall or don't need much light, and as you go higher up, you find plants that need more light. There are also the trees where different vines and fungi can grow.