I'm okay with the first part, but I'm not sure if I totally understand what it does imply (starting from therefore), in conciseness:
1- How does a path existing with finite resistance between the output and supply or ground help with the low output impedance?
2- What does it mean for the inverter (a digital circuit) to have low output impedance? In analog circuits like the common-source/common-drain amplifier it meant that it can drive heavy loads (e.g. a large capacitance or at high frequency)
3- How does it help make it less sensitive to noise and disturbances?
I have one more question that I would be also happy if I get the answer to, the book also states that because the high and low output levels are equal to supply and ground voltage respectively, we know that it has a high noise margin, does knowing the fact about output voltage levels alone help us talk about the noise margin because I don't it feel that it says enough?
Thank you :)).