What is the difference between electric field and electric field intensity? I have read in my text book that electric field is the space or region around a charge in which an electric test charge would experience an electric force, while intensity is the force per unit charge. What is the difference between both, aren't both same?
 A: The electric field is a vector, a quantity that has both a magnitude and a direction. The electric field intensity is the magnitude of the vector.
For example, if we had an electric field vector which extended 1 unit in the x direction and 1 unit in the y direction, then its magnitude would be $\sqrt{1^2+1^2}=\sqrt{2}$ units.
A: It's a little confusing when they say force per unit charge, I know they are referring to a test unit of charge say 1 electron. But the field is also generated by "unit" charges, say 10 electrons, so they should be clear that they are talking about the test charge unit and not the source charge which could be single of many units. – 
A: The electric field acts in different directions. In each direction it acts with a certain strength. Lets say that it acts with $E_x$ in the $x$-direction, with $E_y$ in the $y$-direction, and with $E_z$ in the $z$-direction. The total electric field is now represented by
\begin{equation}
\boldsymbol E=\begin{pmatrix}E_x\\
E_y\\
E_z\end{pmatrix}.
\end{equation}
The total field strength is now given by
\begin{align}
|\,\boldsymbol E\,|&=\sqrt{E_x^2+E_y^2+E_z^2} = E.
\end{align}
