Resistance is the measure of how much an object impedes the flow of electricity. The higher an object's resistance, the less current will flow through it when you expose it to a particular voltage drop. To use the water analogy, resistance resembles a constriction in a pipe. The narrower the pipe (higher the resistance), the harder it is to push water through that pipe. If you keep the water pressure constant (constant voltage drop) as you narrow the pipes (increase the resistance), then less water will flow (the current will drop).