Current doesn’t travel like the OP seems to envision. Think of it more as a tube filled with marbles. Push a marble in one end and another pops out of the other end, but you didn’t push a marble all the way through the tube. Current is kinda like that, except that it’s electrons moving and electrons don’t behave exactly like marbles. The electrons get pushed from atom to atom. Since you can’t magically create electrons to shove into one end of the “tube” (wire), this only works if there’s a “loop”, aka a circuit. The generator doesn’t shove electrons into the end, like the marble example, but instead just causes the electrons to move, leaving holes behind. The electrons all around the circuit all move in one big loop, and when it gets back around to where it started, those moving electrons fill in the holes. Picture a string of atoms in a circle, and the electrons all hopping from atom to atom around the circle. If you break the circle, the electrons can’t hop across the gap, and everything stops.
We use AC instead of DC because wires aren’t superconductors. Since wires aren’t superconductors, electricity going through them gets turned into waste heat. If you are trying to move a lot of electricity from one place to another and you have a really long distance to go and a lot of wire, that wire generates a lot of heat and a lot of that electricity gets wasted. The amount of electricity that gets wasted in heat is proportional to the current that goes through the wires, not proportional to the total energy that goes through the wires. The total power, which is current times voltage, has to stay the same. If you make something that can double the voltage, then the current will be cut in half. If you can make the voltage 10 times bigger, then the current will be 1/10th.
This device that steps the voltage up or down is called a transformer, and this is why we use AC instead of DC to overcome resistance in the wires. An AC transformer is just two coils of wire around a hunk of iron. There is no simple DC transformer. In the old days, they could make DC transformers by using a motor connected to a generator, but that wastes a lot of energy spinning the motor/generator set, and a motor/generator set is a lot more expensive than two coils of wire around a hunk of iron. These days we can make DC transformers using high power semiconductors, but still, they aren’t cheap. AC transformers are always simpler and cheaper.
So here’s how it works. You step up the voltage by a factor of say 100. That steps the current down by a factor of 100. The electricity lost in the wire is proportional to the current squared, so you reduce the electricity lost in the wires by a huge amount. Then at the other end, you step the voltage back down by a factor of 100 so that it’s back to what it started as, and the current gets stepped back up by a factor of 100 so that your overall power going through the system is the same. Sure you’ve made the system more complex by adding transformers, but now you can move the electricity from one place to another over distances without a huge loss in the wires.
This is exactly what Edison and Tesla/Westinghouse ran into. Edison’s DC systems for electric lighting only worked in areas where the lighting ran for short distances, because at longer distances the system just lost too much energy in the wires and the lights were too dim. By using transformers all over the place, Tesla and Westinghouse were able to light up entire towns even when the buildings and houses were farther apart.
So that’s what we use today. Power from the generating plant is stepped up to very large voltages by transformers and are sent over power “transmission lines”, which are those big metal towers. The voltages there are typically anywhere from about 50,000 volts to half a million volts and higher. At the end of the transmission line, the voltage gets stepped down using transformers at a substation, and is sent out through “distribution lines” which distribute the electricity through the buildings and neighborhoods. Distribution lines are the type you see on wooden telephone poles, though more and more often they are now being built or moved underground. Distribution lines typically operate at somewhere between 3,000 and 12,000 volts, though some are a bit higher than that. All along the distribution lines, individual transformers step the voltage down to 120/240 volts (it’s called a split phase transformer) which then typically feeds three or four houses. If you have overhead lines in your neighborhood, the transformers are big metal cans that hang on the poles. If your distribution lines are underground, the transformers will be in big metal boxes on the ground.
DC does have some advantages over AC. With AC, you lose energy due to capacitance and inductance in the wire, which you don’t lose with DC. Also, AC power lines have to be designed for the peak voltage of the AC sine wave, but you effectively only get the RMS value out of it for its effective energy. A DC power line can always run at peak voltage. It doesn’t vary in a sine wave like AC does. What this means is that you can push more power through the same wire using DC instead of AC. But, even with modern technology, there’s still no simple DC transformer. Switches also are easier to use with AC instead of DC. At high voltages, when you open a switch, the electricity tends to draw an arc. With AC, the sine wave goes to zero twice during each sine wave cycle, which will naturally extinguish this arc. DC is constant, which means that the arc doesn’t naturally extinguish, requiring some fancier and more expensive switch designs to make it work.
What this means is that at short distances, the cost of DC transformers and switchgear is too great, and you don’t save enough money with your wire and insulation standoffs etc. costs to make DC worthwhile. At longer distances though, you save enough in wire/insulators and extra power going through the line that you can offset the extra costs of the transformers and switchgear, making long distance DC power transmission actually cheaper than AC. AC also loses a huge amount of power due to inductive and capacitive losses when going through underwater cables, so DC is often used for underwater lines even when the distances are shorter.
This is all a bit technical, so if I didn’t explain something very well, feel free to ask questions.