Schneider Electric CSW120 Surface Mount 1 Gang 2 Way Switch is designed to control the flow of electricity to a light or other electrical device from two different locations. It is designed to be installed on the surface of a wall or enclosure, rather than recessed into it. It's often used when it's not feasible or practical to install a switch in a wall cavity.

1 Gang is the number of switch openings in the plate. It is a single-gang switch, meaning it accommodates a single switch.  20A-16AX is the current rating and switching capacity of the switch. The switch can handle a maximum current of 20 amperes. 16AX is the maximum current the switch can safely break or make. It means that it's rated for switching inductive or motor loads of up to 16 amperes. 

250V is the maximum voltage that the switch is rated to handle. It's a standard voltage for household electrical systems. IP66 is an Ingress Protection (IP) rating. It indicates the level of protection the switch provides against dust and water.

In summary, Schneider Electric CSW120 Surface Mount 1 Gang 2 Way Switch is a sturdy and versatile surface mount switch suitable for outdoor or harsh environments where there might be exposure to dust and water. 

Features

• IP 56/66 rating / 16 up to 40A / 250 up to 500V / SP up to TP
• Neat & compact modern design
• Large switch actuator provides easy switching even with gloved hands
• It is made of heat-resistant polycarbonate