What is Styrofoam?
Styrofoam Brand Foam is a patented product of the Dow Chemical Company. In 1941, Lab experiments produced polystyrene foam. The Dow Chemical Company was able to patent this technology and called it Styrofoam.

Styrofoam is moisture-resistant and unsinkable, which made it an attractive choice to build six-man rafts in 1942 for the United States Coast Guard. The United States Coast Guard and Navy were able to find additional war time applications for Dow’s new product until new uses were found in the late 40’s.

Styrofoam is often used to refer to coffee cups, coolers and packing material. However, these items are only generic foam and none have ever been made from true Styrofoam. Decades of the word being misused has caused the everyday meaning of Styrofoam to refer to coffee cups, coolers, packing material, et al. An important difference is that true Styrofoam is light blue in color; where as the other generic types of foam are typically white in color.

In 1949, Styrofoam was used to insulate roofs and later used to insulate the underneath of highways in 1966. The technology that created Styrofoam was continually tested and improved throughout the years. Eventually Styrofoam Brand Insulation was utilized for insulating foundations in the 1970’s. Throughout the 1980’s and 1990’s, Dow Chemical Company has remained selling their popular Styrofoam products throughout the world. After the turn of the century, Dow chemical company further improved their product by making it termite-resistant.

In addition to its application in building and wartime, Styrofoam is also popular for crafts. There are numerous ways for crafters to work with Styrofoam such as cutting, painting, gluing, sanding and sculpting. Styrofoam is also used for home décor and floral designs. For more intricate projects and designs, Styrofoam can be cut with cookie cutters, curled and used as a base for texture projects.
There are many advantages for home and floral designers and crafters to use Styrofoam on their projects and designs. Styrofoam cuts easily and stays true to shape and size without any gaps or wholes throughout the product. Because the foam is closed cell, it will not absorb any water. Styrofoam is also lightweight, easy to handle, reusable, and retains it shape even when wet. Another common misconception is that Styrofoam is not recyclable. It is true that Styrofoam is not biodegradable. However, it does not contain any chlorofluorocarbons (CFCs) and it is 100% recyclable.

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Jack... that is a lot of information, but still... what is it actually made from? I was told oil.

Well, it's a polystyreme foam ... a hydrocarbon, obtained by way of the petroleum industry ...

Polystyrene (IUPAC Poly(1-phenylethane-1,2-diyl)), abbreviated following ISO Standard PS, is an aromatic polymer made from the aromatic monomer styrene, a liquid hydrocarbon that is commercially manufactured from petroleum by the chemical industry. Polystyrene is one of the most widely used kinds of plastic.
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"Styrofoam" which is a brand name -
is made of polystyrene - which is a non-biodegradable
"be here when nothing but the cockroaches are" plastic.

From Wikipedia:
Polystyrene is a rigid, brittle, inexpensive plastic that has been used to make plastic model kits and similar knick-knacks. It would also be the basis for one of the most popular "foamed" plastics, under the name styrene foam or Styrofoam. Foam plastics can be synthesized in an "open cell" form, in which the foam bubbles are interconnected, as in an absorbent sponge, and "closed cell", in which all the bubbles are distinct, like tiny balloons, as in gas-filled foam insulation and flotation devices. In the late 1950s, high impact styrene was introduced, which was not brittle. It finds much current use as the substance of toy figurines and novelties.

the basis of most-any plastic is petroleum.

Aha!! Now we're getting somewhere....