What is ABS Plastic?
bricks are made from ABS plastic. 😊

A summary of the answer found on a creativemechanisms.com blog is offered below: 

ABS (Acrylonitrile-Butadiene-Styrene) is an opaque thermoplastic.
Thermoplastics can be heated to their melting point, cooled, and re-heated again without significant degradation. Instead of burning, thermoplastics like ABS liquefy which allows them to be easily injection molded and then subsequently recycled.

Strong and durable even at low temperatures, it offers good resistance to heat and chemicals and is easy to process.

The most important mechanical properties of ABS are impact resistance and toughness. A variety of modifications can be made to improve impact resistance, toughness, and heat resistance. 

How is ABS made?
ABS is most commonly polymerized through the process of emulsion (the mixture of multiple products that don’t typically combine into a single product). A well known example of an emulsified product is milk.

It is important to note that because ABS is a thermoplastic material, it can be easily recycled as mentioned above. This means that a common way of producing ABS plastic is from other ABS plastic (i.e. making ABS from ABS).

Is ABS toxic?
ABS is relatively harmless in that it doesn't have any known carcinogens and there are no known adverse health effects related to exposure to ABS

What is ABS used for?
There are countless applications for ABS. Among the most widely identifiable are keys on a computer keyboard, power-tool housing, the plastic face-guard on wall sockets, and LEGO toys. 
ABS is very structurally sturdy, which is why it is used in things like camera housings, protective housings, and packaging. If you need an inexpensive, strong, stiff plastic that holds up well to external impacts, ABS is a good choice.
Industry wide, it’s known for its very good chemical resistance within corrosive environments.
Not surprisingly, polypropylene is used more widely for durable goods production than any other plastic in the United States. Generally speaking, durable goods are things that are not simply thrown away after use (as compared to a non-durable goods like plastic water bottles or Wal-Mart bags).

Why is ABS used so often?
ABS has a strong resistance to corrosive chemicals and/or physical impacts. It is very easy to machine and has a low melting temperature. ABS is easily machined, sanded, glued and painted. This makes it a great material for prototyping. You can also get good cosmetic finishes with ABS and it can also be colored relatively easily, unlike some other plastics. This is a reason it is often used for enclosures (housing) that might have different textures or glossy surfaces. All of these characteristics lead to ABS being used in a large number of applications across a wide range of industries.

When is is ABS not as popular?
ABS plastic is not typically used in high heat situations due to its low melting point. Despite it being relatively harmless, in that it has no known carcinogens and no known adverse health effects related to exposure, ABS is typically not suitable for medical implants.
ABS polymers are soluble in esters, ketones, ethylene dichloride and acetone (some nail polish removers are acetone and would damage ABS surfaces).