What is the difference between micro-inverters and string inverters?

Inverters convert the DC voltage provided by the solar panel into usable AC power.  The string inverter accepts DC power from a “string” of many solar panels wired to a large single inverter which produces power from all the panels.  The micro inverter is a small inverter generally attached to the rail under each panel that converts power from a single solar panel independently.  Therefore the micro-inverters function more efficiently where shading is an issue but are more expensive than standard string inverters.  String inverters are an older more well tested technology although may not be as efficient.