An
inverter makes AC power; in an RV, this means it takes in 12V DC power (such as from the battery) and makes 120V AC power (to run household-style appliances).
A
converter could convert any form of
electrical power to any other, but in an RV the term nearly always means a device which takes in AC power (from the campsite services or a generator) and makes 12V DC power, to run stuff in the trailer and possibly to charge the battery.
A battery
charger is a specific type of converter which is intended to charge a battery, and should manage the power supplied to it. A converter can incorporate a battery charging feature.
Older trailers normally have a converter (my
Boler does), which in only some cases charges the battery (it was an option for my
Boler and I don't have it). Some newer RVs have in inverter, often in combination with a converter with battery charging capability. More commonly, people use separate general-purpose inverters - I have two, and intend to mount one in the
Boler, but have not yet.
Converters are usually on whenever the AC power cable is plugged in, but some require the user to flip a
switch to go between 12V DC power from the converter and power from the battery. With mine, the switch is automatic, whenever the converter is supplied with power, but I can turn off the converter with the circuit breaker which supplies it - the breaker panel is right beside the converter.
I suggest using the Search feature in this forum (see the link near the top right of the page) using some of these keywords, since there has been lots of good information posted.