Do capacitors increase voltage

Capacitors store charge. The formula is Q=CV. They do not by themselves increase voltage or current.

If a capacitor is connected to a load, it can provide a large transient current in respond to sudden demand. It can only average out demand spikes, it cannot provide more current on average than is available from the supply.

In a circuit such as a power supply, a capacitor can store charge, and hence preserve an output voltage, during periods when the input voltage falls e.g. at zero-crossing of an AC supply.

It can also be used in a voltage-doubler or inverter circuit, possibly together with an inductor, to generate a high voltage from a low one. But it, by itself, does not increase voltage, it merely collects charge like a funnel collecting raindrops to provide a steady stream of water.

Electrikals...