Four factors affect the capacitance of a capacitors:

1. Area of the plate
2. Distance between the plates
3. Type of dielectric material
4. Temperature

A capacitor is either fixed or variable. A fixed capacitor has a definite value that cannot be changed. A variable capacitor is one whose capacitance can be changed either by varying the space between plates (trimmer capacitor) or by varying the amount of meshing between two sets of plates (tuning capacitor).