I think this schematic has the potential of making it clear to me. Thank you for showing it to me. Just a couple questions then:If I put a voltage on the base of Q1, Q1 draws current which raises the emitter voltage of both transistors causing the collector voltage on Q2 to rise. If I do the same to Q2 the emitter voltage on both transistors will rise and the collector voltage of Q1 will rise. The collectors of Q1,2 are the outputs of the differential amplifier. In an OP-Amp these outputs continue on to a push-pull output stage that has a single ended output.
So, voltage to Q1 raises the collector current of Q2 and vice versa and we "read" the voltage from those collectors somehow connected into one output. That's cool. I can see the differential amplification! The only thing I still don't see is how the first "golden" rule explained by this? Namely:
The output attempts to do whatever is necessary to make the voltage difference between the inputs zero.