does a resistor slow down the flow of electrons or just let less electrons through? or is it both? I like to have an intuitive grasp of whats happening our tutor said they 'resist' the flow of electrons but I want to understand exactly whats happening.
 A: What's the effect of a resistor? It's a component that dissipates energy end thus lowers the voltage.
So what is voltage? It's the strength of the field that moves the electrons, while current represents the number of electrons flowing through the wire. Free electrons can be stopped all together or slowed all together, but it's not possible to select only some electrons to be stopped. They all feel the same field.
There is another reason why it's not possible, or at least practical, to lower the number of electrons. In this case the "resistor" should take away the particles from the flow and store them somewhere, for example by binding them on atoms. You can see the major problem here: in little time the resistor would be completely full and will stop working. Ejecting the electrons appears to be a solution, but that would interfere with the rest of the circuit and I don't think the general public would feel very excited about resistors that behave like $\beta$-emitting radioactive nuclei. ;)
I hope the answer is clear enough.
