A capacitor is physically made up of two conductors and between every two conductors there is some capacitance.
The capacitance between any two conductors is basically a measure of their capacity to store charge at the cost of a voltage between them.
If we take two conductors and add positive charge to one of them and negative charge to the other, as illustrated in Figure 5-1, there will be a voltage between them. The capacitance of the pair of conductors is the ratio of the amount of charge stored on each conductor per voltage between them:
C = the capacitance, in Farads
Q = total ...