Gravity walls are low walls that resist the forces of soil through the weight and set-back of the blocks. A gravity wall can stand on its own with the help of some basic steps. Gravity walls are typically 2-3 feet (600mm - 900mm) high and recommended for do-it-yourselfers.
Reinforced walls are tall walls commonly found in commercial applications that require an engineer, contractor, soil testing and reinforcement fabric. A reinforced wall can go as high as 40 feet (12.2 meters). If you want to build a reinforced wall, you need to hire a contractor.