Casting involves pouring molten metal into a mold to create shapes. It is an economical process for producing complex shapes in a single piece, especially for low production runs or large products. Key factors that influence the casting process include solidification rate, flow of molten metal, heat transfer during cooling, and properties of the mold material. Proper gating system design is important to avoid defects from shrinkage and porosity during solidification as the metal cools and contracts.