Usually, as the fertilized egg within the ovule develops into an embryo, the ovule walls convert to a seed coat, turning the ovule into a seed or ripened ovule.
The seed cover protects the inside from injury or drying and it is used as nourishment until the seedling can process food on its own.
The germination of seeds depend on the temperature and moisture of the environment; in particular, warmer temperatures are usually necessary for germination and seedling growth; although for some seeds to successfully germinate, they need cool temperatures.
During the germination process, the seed absorbs water, a root pushes through the seed coating; and finally, a shoot pushes up trough the soil and forms a tiny leaf.
Energy for germination is contained within the seed, but such energy for growth after germination comes through the leaves.