If you are plugged into
shore power when you are in a marina,you can run 110v
appliances on the
boat like a microwave without any
equipment.
You generally want the shore power to also charge your 12v
batteries. This is what a
charger does.
When at
anchor you have no shore power. You can use an
inverter to convert the 12v to 110v. There are limitations with this, a microwave for example uses a lot of power, so the batteries would flatten very quickly.
A
charger is no use at
anchor.(unless you have a generator)
When at anchor if you need to charge you batteries you can run the main
engine and/or use
solar and
wind to charge the batteries. Solar and wind cannot be directly connected to batteries and need a
regulator (sometimes its called a controller, but its the same thing)
Hope this simple explanation helps. Some large boats also have a
generator which gives them other options. A
generator is a
motor and
electronics that will generate 110v. This can be used to charge the batteries and run the microwave, just like shore power, but you have the
noise, cost and
maintenance associated with another
motor.