Those are air variable capacitors. The finned plates are charged using air as a dielectric. Turning the knob changes how much area the plates have to work with, thereby changing capacitance. The one on the left is 3 ganged, 2 on the right. This is so separate circuits can be simultaneously tuned to tune in a signal and adjust the local oscillator(s) to mix and form an intermediate frequency.

In the center is a varactor, an early one actually, which is basically a reverse biased diode which changes capacitance with the magnitude of the reverse bias voltage. My QRP radio uses one, the microprocessor reads the optical encoder on the tuning knob and sends out an analog voltage that adjusts the LO via a varactor.

The big one is oil filled. The square one is very old, you don't see those anymore. The black one that looks like a resistor is an old "black beauty" capacitor valued by audiophiles.

I'm not stupid about math, physics, electronics, etc. Intelligence is not a singular quantity, folks have strengths and weaknesses in different areas. No amount of training would allow me to do what Gia or Holly does, I just don't get those kinds of compositions.