How a Grid-tied Micro-inverter Solar System Works

What's the difference between a stand-alone, off-grid solar system and a grid-tied solar system?  

Off-Grid - An off-grid system provides power for your house when the sun is up and also stores power in batteries for later use when then the sun is down.  These systems require a charge controller that controls the charging of the batteries and an inverter that converts the DC power from the solar panels and the batteries into AC power for your house.  These systems are expensive and complex to install and maintain.  They  generally only provide a small amount of power because of the expense of larger systems.

Grid-Tied -  These systems convert the solar power from you panels directly into AC power.  The power produced is fed into your house electrical panel and provides power for all your household needs.  Any excess power automatically flows out of your house, spinning your meter backwards.  This eliminates the need and expense of a charge controller and batteries.  As the sun goes down you slowly switch from sending power to the grid to taking it back, the meter keeps track of the difference.  Over the course of a year there will be sunnier and cloudier periods as well as the length of the day changing.  Your goal is to provide most the power you will need throughout the year.