Transistor PNP 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.
LDR A transducer which converts brightness (light) to resistance (an electrical property). LDR = Light Dependent Resistor
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
Light Emitting Diode A transducer which converts electrical energy to light. Usually abbreviated to LED.