Electric utility companies refer to residential grid-tie solar power arrays as distributed generation (DG) generators. They use this term because your solar panels are producing and distributing electrical power back into our utility grid.
Islanding refers to the condition of a DG generator that continues to feed the circuit with power, even after power from the electric utility grid has been cut off. Islanding can pose a dangerous threat to utility workers, who may not realize that a circuit is still "live" while attempting to work on the line. Distributed generators must detect islanding and immediately stop feeding the utility lines with power. This is known as anti-islanding. A grid-tied solar power system is required by law to have a gridtie inverter with an anti-islanding function, which senses when a power outage occurs and shuts itself off.
One common misconception is that a grid tied system will continue to generate power during a blackout. Unless there is a battery back-up system, the gridtie solar system will not produce power when the grid is down.