I don't know why nobody seems to ever begin with: A filter is a voltage divider with frequency-dependent complex impedance.
If you can calculate what a resistor network does, or get a computer to do it, you can also calculate what a filter does (and you'll definitely want a computer for that).
(Going backwards, from a desired frequency response to a filter design, takes more learning. Luckily some very smart people already designed filter templates where you can just plug in the frequency you want)
this is exactly how I intuitively approach filters as an applied engineer. Does it give a ground path to DC (low frequencies) and pass the higher frequencies, or vice versa. If we change the capacitance how does the frequency response of the divider change?
If you can calculate what a resistor network does, or get a computer to do it, you can also calculate what a filter does (and you'll definitely want a computer for that).
(Going backwards, from a desired frequency response to a filter design, takes more learning. Luckily some very smart people already designed filter templates where you can just plug in the frequency you want)