The picture shows a magnet near a coil of wire. The coil is connected to a sensitive meter which shows zero current.
If we push the magnet into the coil, the meter flicks to the right.
If we pull it out again, the meter flicks to the left.
Pushing it in and out makes the meter flick left then right.
We call this effect electromagnetic induction. We are inducing a voltage by moving a magnet in a coil.
Notice that when the magnet is stationary, there is no voltage. This makes sense: we have to put some effort in to get a voltage out. If we don't put anything in, we don't get anything out.