Combining capacitors in series reduces the total capacitance, and isn't very common, but what are some possible uses for it? It shouldn't be used to increase the voltage rating, for instance, since you can't guarantee that the middle will be at half the DC voltage of the total, without using bleeder resistors.
The capacitance doesn't increase in series; it decreases. Capacitors in parallel are capacitors that are connected with the two electrodes in a common plane, meaning that the positive electrodes of the capacitors are all connected together and the negative electrodes of the capacitors are connected together.
Every capacitor will 'see' the same voltage. They all must be rated for at least the voltage of your power supply. Conversely, you must not apply more voltage than the lowest voltage rating among the parallel capacitors. Capacitors connected in series will have a lower total capacitance than any single one in the circuit.
Note - When capacitors are in series, the total capacitance value is always less than the smallest capacitance of the circuit. In other words, when capacitors are in series, the total capicitance decreases. It's always less than any of the values of the capacitors in the circuit. The capacitance doesn't increase in series; it decreases.
Thus, if you need to have a capacitor in a high voltage circuit it may be necessary, or just more convenient, to place them in series. Recovering the nominal capacitance of the individual capacitor, if needed, is a question of building up an array of them in parallel.
Capacitors in series are versatile and valuable configurations for various electronic applications. By understanding the principles of capacitance, voltage distribution, energy storage, and the influence of dielectric materials, one can harness the full potential of capacitors connected in series.