The water-and-pipes analogy helps out here: Current is similar to the amount of water flowing through a pipe. Voltage is similar to the water pressure. Resistance is similar to the width of a pipe — the smaller the pipe, the larger the resistance.
So the more water pressure you have, the more water that flows through the pipe. The smaller the pipe, the less water that flows through it. The amount of water flowing through a pipe (the current) is directly proportional to the water pressure (the voltage) and inversely proportional to the skinniness of the pipe (the resistance). In electricity, you can calculate how much current is flowing through a circuit if you know the voltage and the resistance.
Resistance — the tendency of a substance to impede the flow of electrons — is measured in ohms, named after Georg Simon Ohm (1789–1854), who also proposed the famous Ohm’s Law. The law states I = E / R where I is traditionally used to represent current in amperes, E is used to represent voltage (it stands for electromotive force), and R is resistance.
— Code (Charles Petzold), Loc. 520–9