1. Converter - Allows you to run your 12 Volt system while plugged in to shore power. The newer units also have smart battery
charging circuits, which will charged your battery
while plugged into shore power.
2. Inverter - Allows you to run 120 Volt items using your 12 Volt battery. Only good for running small items for short periods of time. Large items will drain the battery quickly.
3. LED lights
, as with many things, have pluses and minuses. The plus side they are energy saving. The negative side, by nature they are quite directional and sometimes the color isn't as pleasing.
4. Plugs? I assume you mean outlets. 12 Volt outlets or 120 volt outlets?