How does the CD4066 Work?
You can regard the 4066 as 4 relay contacts but there are a bunch of constraints that limit this analogy. The main ones are: -


On resistance is massively higher than a relay contact (typically 125 ohm)
Ohmic linearity with input signal voltage means signal distortion may occur (unlike normal relay contacts).
Any input / output signal must be constrained to the power rails of the device. In other words, there is *some" isolation capability that is useful but don't expect truly AC signals to do anything other than either badly distort or burn the chip.
Maximum current is limited to a few mA
Open circuit capacitance is quite high thus limiting the ability to "open-circuit" high speed signals.