Rubber is an elastic hydrocarbon polymer which occurs as a milky emulsion (known as latex) in the sap of a number of plants but can also be produced synthetically.
Synthetic rubber comprises the polymerisation of a variety of monomers to produce polymers. These form part of a broad study covered by Polymer science and Rubber technology.
The major commercial source of natural latex used to create rubber is the Para rubber tree, Hevea brasiliensis ( Euphorbiaceae). This is largely because it responds to wounding by producing more latex.