How does shore power and battery charging work?

As an RV rookie, just want to clarify: With all the references to the Pebble “hooked up to shore power,” are we actually talking about having the charger hooked up to shore power, charging and/or maintaining the Pebble battery, which runs everything?

Is there no way to bypass use of the battery (i.e. actually using shore power), so we are always charging/depleting the battery? And how do you typically limit battery charging to the optimal 70–80% instead of constantly charging to 100%, then unplugging?