You haven't posted your complete sketch so I have no idea where the value in "x" comes from.
If "x" is the value obtained from analogRead() then it will be a number proportional to the voltage on the Analog Pin. For example if the voltage on the pin is 5V x will be 1023. If it is 0v x will be 0. If it is 3.7v x will be 1023 / 5 * 3.7 or 757 (approx).
...R