Flowering plants and cone-- bearing plants are able to reproduce sexually and the seed is the result--an offspring that has the potential to form a new plant. Therefore seeds are important to plants because they insure that the gene pool will continue to the next generation.
In flowering plants or angiosperms, seeds are the result of a double fertilization that occurs in the ovule inside the plant's ovary resulting in an embryonic plant and its food supply (endosperm) . This is a triploid food supply resulting from the fertilization of a sperm nuclei and two polar nuclei. The embryo is diploid resulting from the fertilization of an ovum by a sperm nuclei.
Once the seed begins to germinate, the food supply will enable the young plant to survive until it develops a root system and leaves to absorb water and to carry out photosynthesis. Some seeds are able to survive for long periods until they land on a suitable environment due to their seed coat which protects the embryo plant inside. They can also survive during periods of drought or unsuitable temperature until conditions improve.
Some seeds can be produced by self-pollination (if the flower has both sets of sex organs) or by cross-pollination if the flower has separate male and female sex organs. This can help shuffle the genes leading to an offspring with a new combination of traits.