The diagram illustrates the different stages involved in the life of a frog. Overall, frogs have to go through several life phases, starting from eggs, turning into tadpoles and then adult frogs.
The former stage begins with a number of frog eggs called frogspawns which were laid by mating frogs. Afterwards, the frogspawns hatch and become a small tadpole which emerges. This stage ends with these small tadpoles grow bigger and their limbs begin to form. All above steps are under the water.
By the latter stage, including 3 steps, the tadpoles start to grow into young frogs. Although they still live in the water, their tails are shorter than before and their limbs develop significantly. When this young frog becomes mature, it has no tail and its four limbs are fully developed. It is then ready to leave the water and it continues to grow in size. This stage ends with the frog is fully adult and is ready to mate to create a lot of eggs.