Epoxies are widely used for applications adhesives, protective marine coatings, gap fill materials & liquid shims, composites, encapsulants & potting compounds, mold making, conductive or insulative electronic materials, and even high-performance cementitious materials like epoxy-based grouts.  They are generally two components (resin and hardener).  This makes epoxies naturally easy to work with and allows them to be easily modified with a wide variety of additives to achieve high strength, durability, lighter weight, reduced slump, fast cure, and other desirable performance characteristics.