Low pass and high pass filters

The circuit you made is a lowpass filter. The green signal is the filtered signal, the node between the capacitor and the resistor is the filter's output. As we see the filter is outputing an 80hz signal with barely no amplitude changes. That is because 80 hz is inside the lowpass filter bandwidth. Increasing either the capacitor or resistor values will decrease the cutoff frequency thus reducing the filter's bandwidth. Usually the resistor value is fixed and the capacitor value is changed according to the system's specifications. The signal you're taking from the 1k resistor acts as a Highpass filter output but it is not a highpass filter by itself. Why does it act as a Highpass filter? Because it is the difference between the input signal and output signal. On Low frequencies you have a sinusoid at 5V amplitude minus a sinusoid with 4.9 volts approximately, the difference taken by the voltmeter results in a 0.1 sinusoid. Now increasing the input signal frequency results in a low capacitive impedance which makes most of the voltage drops across the resistor, thus increasing the blue signal. If you want to build an actual highpass filter just swap the resistor and capacitor positions. Filters are widely used in telecommunications systems, audio systems and in plenty other electronics systems. A classic example is a radio system, changing the radio's frequency actually means tuning a capacitor inside a bandpass filter!

Wow thank you for such a full explanation, I understand what yours saying... i real life you wouldn’t adjust the frequency, rather you would adjust the capacitor, I’ll change it now. At first I made to separate circuits to show the low and high pass filter, but got lazy and combined them lol. Let me edit this.