Although Plexiglass is a form of acrylic plastic, there are subtle differences between the two types. Plexiglass has the distinction of being harder than normal acrylic which makes it easier to drill and cut without breakage. Additionally, Plexiglass is more chemical resistant than traditional acrylic.
Originally, the word Plexiglass was used as a brand name to refer to acrylic plastic that had been cell cast rather than extruded. Plexiglass gained popularity primarily because the cell casting process results in a hard plastic with fewer impurities than traditionally extruded acrylic. Manufacturing costs for Plexiglass are generally higher than for standard acrylic.