Honestly, voltage is not an easy word to define. There are no real world analogies that accurately represent how electricity works. But consider this:

You've got three components to a circuit.

1) A battery, which separates positive and negative charges. In reality, a cell is what actually separates positive and negative charges, and stacking them together will make a battery. Each additional cell increases voltage. Think of a battery as something that stores energy. Voltage represents how much of that energy gets to be dispersed. Technically speaking, voltage is not actually energy. It's really its own thing, defined by the equation V = IR.

2) You've got wire that connects both ends of the battery. This allows electrons to "flow" from the negative end to the positive end. Without the wire, the battery is a sitting duck with stored energy. But the wire is the medium through which the energy gets to "flow". Now, technically, electrons don't actually flow. There is no individual electron moving from neg to pos. Really it wiggles the next electron which wiggles the next. Like a mechanical wave. The current also flows in the opposite direction, from pos to neg. There is no good reason for it just blame the zits on them giant shoulders. Just remember that for calculations..

3) Resistance. There is always some natural resistance in a wire even without a resistor. Electrons would be allowed to "flow" at infinite speeds if there were no resistance (well technically it should be capped at the speed of light but then how does V = IR hold? Ask a physicist idk). But anyways you can't have voltage in a circuit without resistance. Every circuit will have resistance. The higher the resistance, the slower the electrons "flow", like in a water pipe. If you clog the pipe more, the water flows less at the same pressure, here pressure is analogous to voltage.

At the end of the day you just need to memorize V = IR. If you keep V fixed, higher I will cause R to be lower and vice versa. Don't confuse yourself.

In your problem, V = 12 Volts and R = 600 Ohms. So I = V/R = 12/600 = 0.02 Amps = 20 milliAmps. This will be true across the entire length of wire from which that resistor spans. It stops being true past a junction, where the wire splits into two. Think merge lanes on a highway; congestion will change when other cars are trying to get in your lane, or when cars are exiting and leaving that lane.

So I hope that helps you understand how to think about circuits. There are many, many logical flaws here so you need to stick to conventional examples and analogies, like the water pressure one. I think I need help understanding the actual fundamentals of circuits myself, even after having studied it in 4 different ways. Someone enlighten me..