How does a capacitor function in a 120v ac motor circuit?

I dont understand the direction of current flow when a capacitor is wired in series with the start windings in, say, a fridge or ac motor running on der 120v ac. Wiring diagrams seem to suggest that voltage energizes the hot leg of the circuit and current flows through the run windings and then returns via the neutral leg. Without a capacitor, the same thing would happen to the start windings. Problem there I guess is that both windings would be in phase and thus no spin created for the rotor. So, a cap is wired in series with the start windings which I kind of understand. But I dont know how the voltage and current behave. Does voltage energize the hot leg,flow through the start windings and then charge the cap? And then when voltage on the hot leg oscillates down to zero, does the cap discharge back toward the starter windings. Or does current flow through the cap to the neutral leg? Basically I don,t understand where the cap's charge goes when the hot leg is hot and when it is not. Lastly, is the cap placed between (downstream from)the start windings and neutral, or could it be wired between incoming voltage and the windings? Many thanks, scott