Timer(input capture) with STM32 

I understand if you are interested in counting rising or falling edges then setting up the timer as a capture-compare makes sense... however, #1 How does the prescaler value affect the counting? Is it only for __HAL_TIM_GET_COUNTER ? #2 I assume enabling the interrupt will cause it to fire whenever there is a rising edge, but won't it count without using any interrupts? i.e. via __HAL_TIM_GET_COMPARE?