A rubber band is a short length of rubber

Rubber

Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...

 and latex

Latex

Latex is the stable dispersion of polymer microparticles in an aqueous medium. Latexes may be natural or synthetic.Latex as found in nature is a milky fluid found in 10% of all flowering plants . It is a complex emulsion consisting of proteins, alkaloids, starches, sugars, oils, tannins, resins,...

 formed in the shape of a loop and is commonly used to hold multiple objects together. The rubber band was patented in England

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

 on March 17, 1845 by Stephen Perry

Stephen Perry

Stephen Perry was a 19th century British inventor and businessman. His corporation was the Messers Perry and Co, Rubber Manufacturers of London, which made early products from vulcanized rubber. On March 17, 1845, Perry received a patent for the rubber band.- See also :*Other people surnamed Perry...

.
Rubber bands are made by extruding the rubber into a long tube

Cylinder (geometry)

A cylinder is one of the most basic curvilinear geometric shapes, the surface formed by the points at a fixed distance from a given line segment, the axis of the cylinder. The solid enclosed by this surface and by two planes perpendicular to the axis is also called a cylinder...

 to provide its general shape, putting the tubes on mandrel

Mandrel

A mandrel is one of the following:* an object used to shape machined work.* a tool component that grips or clamps materials to be machined.* a tool component that can be used to grip other moving tool components.- Variants :...

s and curing the rubber with heat, and then slicing it across the width of the tube into little bands.
While other rubber products may use synthetic rubber

Synthetic rubber

Synthetic rubber is is any type of artificial elastomer, invariably a polymer. An elastomer is a material with the mechanical property that it can undergo much more elastic deformation under stress than most materials and still return to its previous size without permanent deformation...

, rubber bands are primarily manufactured using natural rubber because of its superior elasticity.

Natural rubber originates from the sap of the rubber tree.