The best way to start to understand electricity is to compare it to water. Voltage is the pressure behing the water and current (amperage) is the amount flowing through a pipe.
Attach a small hose to the bottom of a bucket of water. Lift the bucket of water higher and it increases the pressure which results in increasing the flow (current). This is like raising the voltage.
Placing a resistor in the line is like placing a restrictor in a water pipe, it decreases the flow.
The most basic law of electicity, Ohm's law, is:
Voltage equals Current times Resistance or V=I*R (I=V/R, R=V/I). Increasing the voltage increases current flow, increasing resistance decreases current flow.
Hope this helps. It is the starting point for understanding electricity.