If two of the hydrogen atoms are removed and the carbon atom decides to bond with two other carbon atoms then it can be seen how long chains can be formed.
A carbon atom bonded to 2 hydrogen atoms can be considered a building block or unit of the polymeric chain. These units make up monomers, which are repeating units in the molecular chain structure.
A series of monomers bonded together to form a molecular chain is known as a polymer. The polymer shown is known as polyethylene.