I am an electronic student currently. in class we are learning about low and high pass filters.

I understand that in a low pass filters, the resistor is first and then the capacitor.

In a high pass filter, it is the capacitor first and then the resistor.

I'm trying to understand why there is this difference in circuitry.

I understand that low pass allow only frequencies to a certain point (frequency cut off) to pass through, and high pass only let certain high frequencies pass through but not low frequencies. I also understand that the higher the frequency, the low reactance (resistance) the capacitor has and vice versa. despite knowing this when I look at the circuit and have no idea why low pass has resistor first and then capacitor and vise versa for high pass.

If anyone can help me understand that would be much appreciated. I don't know if it makes a difference, bur we are using AC as the power source.