The diagram shows a simple circuit of a battery, wires, a switch and a lamp. The switch works by breaking the circuit.
An OR gate can have two or more inputs. The output of an OR gate is true when at least one of its inputs is true.
Transistor NPN A transistor amplifies current and can be used with other components to make an amplifier or switching circuit. This symbol is for a bipolar junction transistor (BJT), the type you are most likely to use at first.