Electricity is the flow of charge
A negatively charged particle has more electrons then protons. A positively charged particle has more protons than electrons. In order to measure charge, we can use the unit Coulomb(C). But it is a large unit. To get a charge of 1 C you need a shortage of $6.25 \times 10^{18}$ electrons.
Static electricity is the imbalance of electrons within or on the surface of materials or between materials.
$$ q= ne $$
q is the charge
n is the number of electrons
e is the charge of an electron($1.6\times 10^{-19}$)
Current is the measure of the rate of flow of charge.$^2$
$$ I=\frac{q}{t} $$
t is the time
Applying coulomb formula,
$$ I = \frac{ne}t $$
Current is measured in ampere(A). 1 amp is defined as when the charge of one coulomb flows for one second.
Positive to negative is the the conventional current. This is used.
Negative to positive is the Electron Current.
Potential difference, also called as voltage, is the amount of work done in order to move a unit of charge from one terminal to another.