Current

From Electronics Wiki

Electric current is the flow of electric charge.

The SI unit of current is the ampere, equal to a flow of 1 coulomb per second. Current may be measured with an ammeter, placed in series with the circuit under test. Most digital multi-meters have a current setting.

DC stands for direct current; and AC stands for alternating current.

in a DC circuit, you may also calculate the current flowing, using the formula I = V/R, where V is the voltage drop across a component, and R is the resistance of the component.