I see a lot of circuits where a capacitor and resistor are in parallel. I understand that this causes the capacitor current to be 90 degrees out of phase with the resistor and the rest of the current source. I don't understand why this is useful in either a DC or an AC circuit. I ran it in a simulator, and it seemed to cause slight gyrations in a DC circuit (very slight), but beyond that I don't see what it does. Even with those slight gyrations, I don't see the practicality -- especially when the capacitor just branches off enough to be parallel and then is fed back in on the other end of the resistor. Any help is appreciated. Thanks.