Socket heads are mechanical tools used for tightening or loosening bolts and nuts. They come in different types: impact sockets, designed for heavy-duty use with impact wrenches; standard sockets, for hand tools; and combination sockets, offering multiple functions in one tool. Sockets can be sold individually or as kits with multiple sizes, often including adapters, extensions, and accessories to facilitate work. Impact and standard sockets provide precise torque transfer and durability for professional or DIY use.