Moab IV was the inhabited fourth planet in the Moab system. This system was located within the Moab sector. This was a large, barren planet, and was the site of the human Genome Colony. The colonists left Earth before the introduction of transporters in the 2150s and the colony was founded in 2168 on the planet's southern continent.
In 2368, the location of Moab IV was labeled on its orbital path around Alpha Moab on a system map that was seen in the laboratory of Hannah Bates on Moab IV. (TNG: "The Masterpiece Society", set artwork)
The planet itself was entirely uninhabitable and only the biosphere constructed for the colony allowed for Human settlement. The biosphere, which was built to withstand the harsh environment of the planet, had defensive shields that could increase in strength and had built with materials that could resist earthquakes up to 8.7 on the Richter scale. In the biosphere, the environment was lush and beautiful as well as meticulously maintained. In the 24th century, the colony had several thousand colonists.
In 2368, a stellar core fragment from a collapsed neutron star passed through the sector where Moab IV is located. The passing fragment, which had a density of one hundred billion kilograms per cubic centimeter, posed a serious threat to the colony. Its mass would create large earthquakes, far beyond what the colony was designed to withstand. Because of this unique danger, the isolationist colony made a one-time exception to their policy against outside contact and accepted assistance from the USS Enterprise-D. (TNG: "The Masterpiece Society")
Background information Edit
According to the script, the pronunciation for Moab was "MOH-ub". 
According to the Star Trek: Star Charts ("United Federation of Planets I"), Moab IV (Genome Colony) was listed as a member planet of the Federation in 2378. The author, Geoffrey Mandel, inadvertently listed this planet as Moab VI.