The idea is if you have a specific question about a design, post the schematic and ask the questions. Gives other people something concrete to discuss.
Are you wondering where the signal comes from to start the feedback loop oscillating? Often this arises from transients when the power is first applied, but oscillators which depend on this may not always start reliably. Many good oscillators will start as a result of internal random noise, even if the power supply voltage comes on very gradually.