A gene is piece of DNA containing the information necessary for the synthesis of a functional molecule, usually a protein. Its function can be linked to the development or control of a physiological function. The gene is considered the storage unit for genetic information and genetic inheritance, since it transmits such information to the offspring.
In eukaryotes (slightly more complex organisms with DNA within a nucleus), genes have two types of regions: exons or coding regions and introns or non coding regions. Proteins are encoded only by exons, instead introns must be removed before the information is used to built the protein (gene expression). Prokaryotes, simpler coreless organisms, lack introns.