IGH = Internal gear hub, they have one cog front and back. Like Sturmey Archer hubs. Their 3 speed was invented in 1902. They still work fabulously, the new designs are even better. Very simple to set up and take apart. Their strength is because the spokes have even tension on both sides. They last forever with proper lubing after 3 or 4,000 miles. Lots made in 1950s are still in use.
The absolute BEST no trouble no service brakes are SA DRUMs. Mine has 24,000 miles.