If resistors do not decrease flow in a circuit then why are they able to make things like an LED short when otherwise it would without the resistor
It's not slowing the electrons (charges, actually) down (since they're going into the resistor at the same rate that they're coming out), it's absorbing energy from them and turning it into heat. Volts is joules per coulomb, and since charge is a physical (or physical-equivalent, if you want to get technical) amount, the only way to reduce voltage is to remove energy from the charge.