A component that opens or closes a loop in a circuit is – yup – a switch. An open circuit means that no current flows, aka it’s off. A closed loop means the loop is continuous and current does flow: on.
In electronics, switches have a number of “poles” and a “throws” (we promise we’re not talking about Olympic javelin throwing).
The pole refers to how many circuits a switch can control, and the throw is how many positions a switch has.
Your basic light switch (and our Switch module) are known as “single pole single throw” or SPST. The Double Switch module is know as a “double pole double throw” or DPDT switch because it controls two circuits with two switches (although both switches are controlled by a single slider).