A geogrid is geosynthetic material used to reinforce soils and similar materials. Geogrids are commonly used to reinforce retaining walls, as well as subbases or subsoils below roads or structures. Soils pull apart under tension. Compared to soil, geogrids are strong in tension. This allows them to transfer forces to a larger area of soil than would otherwise be the case.
Macgrid:

MacGrid™ is a geogrid for soil reinforcement, made from high molecular weight, high tenacity polyester multifilament yarns. The yarns are woven on tension in machine direction and finished with a polymeric coating. MacGrid™ geogrids are engineered to be mechanically and chemically durable, and resistant to biological degradation.