What is the difference between voltage and current?

Voltage . . .
the difference in electrical 'pressure' between two points, that makes electrons want
to move from the higher-pressure point to the lower-pressure point if there's something
in between the two points for them to move through.

Under normal circumstances, there can easily be this difference in 'pressure'
between two points, but no electrons are moving across, because there's nothing
for them to move through. For example, there is substantial voltage between the
two slots in a household electrical outlet, but no way for electrons to move from
one to the other, until you plug something into the outlet that provides a path.

If the difference in pressure is great enough, then the electrons lose all reasoning
power and are consumed by an insane desire to make the trip even if there's nothing
there for them to move through, and they jump from one point to the other one anyway.
That's when you see a spark, or lightning.

Current . . .

When there's a path between the two points, then the electrons take off and move
from one point to the other. As long as the voltage is there, more and more electrons
step up and make the crossing. Current is simply the measurement of how heavy the
traffic is on the path ... how many electrons pass any point on the path every second.
If there happen to be about 6,241,000,000,000,000,000 electrons passing by in each
second, then we say that the current is "1 Ampere".

Greater current can be caused by either one of two conditions:

-- Greater voltage between the two points, inspiring more electrons to make the trip.

-- A path made of material that's easier for the electrons to travel in, such as
silver or copper ... the reason that electrical wiring is most often copper wire.