The carbon atom is the central atom in all organic molecules. An enormous variety of organic molecules is possible because carbon is able to bond at four different sites, form long chains, and combine with many other kinds of atoms.
Carbon is unique in that it can combine with other carbon atoms to form long chains.
What is really unusual is that the bonds formation potential in carbon is that these bonds are located at equal distances from one another. These bonding sites are arranged this way because in the carbon atom there are four electrons in the second energy level. Carbon atoms are usually involved in covalent bonds. Carbon can combine with 4 other atoms by forming 4 separate single covalent bonds with other atoms. Some organic molecules contain triple covalent bonds.