At the start the capacitor is fully discharged.
When the switch is closed, the capacitor is charged up from the energy stored in the battery until the capacitor has the same voltage as the battery. At first it charges up rapidly and then gradually slows.
Open switch. The capacitor remains fully charged.
Pushing the RESET button short circuits the capacitor and the energy stored in the capacitor is now discharged, slowly at first. With small capacitors the energy discharge is very fast, almost immediate. With large capacitors, this can take a long time.
This is why capacitors are used in timing circuits.
Think of water flowing through a pipe. If we imagine a capacitor as being a storage tank with an inlet and an outlet pipe, it is possible to show approximately how an electronic capacitor works.
First, let's consider the case of a "coupling capacitor" where the capacitor is used to connect a signal from one part of a circuit to another but without allowing any direct current to flow.
(Image: Capacitor passes AC in coupling circuits)
If the current flow is alternating between zero and a maximum, our "storage tank" capacitor will allow the current waves to pass through.
(Image: Capacitor blocks DC in coupling circuits)
However, if there is a steady current, only the initial short burst will flow until the "floating ball valve" closes and stops further flow.
So a coupling capacitor allows "alternating current" to pass through because the ball valve doesn't get a chance to close as the waves go up and down. However, a steady current quickly fills the tank so that all flow stops.
Now, lets think about the De-coupling Capacitor
(Image: Capacitor bypassing the AC in de-coupling circuits)
Where a capacitor is used to decouple a circuit, the effect is to "smooth out ripples". Any ripples, waves or pulses of current are passed to ground while d.c. flows smoothly.