Re: what is the work of a resistor?

Yes, a resistor does actually resist the flow of electrons (i.e., current).  
Suppose we had a wire with very little resistance, say 0.01 Ohms.  If it were 
connected to your 10 V power source, then according Ohm's law (current = 
voltage / resistance) the current in the circuit is 1000 A.  If the total 
resistance of the circuit is increased to 1 Ohm, then the current is 10 A.  
Therefore, as the resistance increases, the flow of electrons is decreased.  By 
definition, 1 Ampere (A) is present when 1 Volt (V) is applied across a 1 Ohm 
resistor.  As the resistance goes toward zero Ohms, the current goes toward 
infinity.  So, as compared to a circuit with no resistance, all resistors 
resist the flow of some current.