AIO devices combine inverter, solar charge controller, and converter in one device.
While more common on very large RVs with frequent access to pedestal power at campgrounds they are gaining popularity with other RV types.
seamless power
The selling point is the AIO seamlessly takes power from the grid[1] when available, and automatically switches to inverting from battery bank power when the grid isn't available.
In either case, 12vdc[2] is unaffected. The converter function charges the bank and supports DC loads when shore power is present. Solar does these duties when shore power is not present.
gotchas
AIO can be sensitive to shore power inputs, in particular to sine wave collapse sometimes seen from heavily-loaded generators.