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.
Logic gates process signals which represent true (1, high, +Vs, on) or false (0, low, 0V, off). For more information please see the page on logic gates. There are two sets of symbols: traditional and IEC (International Electrotechnical Commission).
An AND gate can have two or more inputs. The output of an AND gate is true when all its inputs are true.
The diagram shows a simple circuit of a battery, wires, a switch and a lamp. The switch works by breaking the circuit.