E is energy (measured in Joules in the S.I. system)

Voltage is energy per unit of charge, the unit is the Volt in the S.I. system.

Charge is measured in Coulombs in the S.I. system. Think of a unit of charge as a busload of electrons (negative charge) or protons (positive charge).

One volt is thus 1 Joule per Coulomb

I is current, measured in Amperes (Amps for short form of the name). Think of it as the amount of charge (busloads of electrons) going past a point in one second.

Power is Energy per unit time, and Power is Very Important P=VI. (energy per unit of charge times units of charge divided by time)

R is resistance, the units of which are Ohms, defined by how much energy it takes to push a unit of charge through it. or Voltage required to produce a 1 Ampere current, or more simply as the ratio of voltage difference lost across the resistor (energy lost per unit of charge) to current produced (units of charge going by in a second). R=V/I which can be rearranged to **V=IR. **

Ohm's law is not the definition of resistance; **Ohm's law** says that for certain materials (not all materials and even **for some materials** not all conditions thankfully) the **Resistance** (which is defined in it's own right as the ratio of V/I quite apart from Ohm's law) **does not change** (i.e. the ratio of V/I is a constant that does not depend on the current or the voltage).

and since power is VI, P is **(IR)**I which is equal to I^2 R.

If you want energy, you will have to multiply P by time.