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.
Resistor A resistor restricts the flow of charge. Uses include limiting the current passing through an LED, and slowly charging a capacitor in a timing circuit. Some publications use the old resistor symbol
Electricity can flow only if there is a complete circuit from the battery through wires to components and back to the battery again.
Microphone A transducer which converts sound to electrical energy.