Portal axle being state of the art? <grin>I don't think so, Tim! </grin> They've been around for years.
The usual run-of-the-mill axles have the axle shaft running in the axis as the wheel, i.e. the wheels bolts directly to it.
In a portal axle, there is a gearbox out at the end of the axle tube. The axle turns a gear in the top of the box, which drives a gear (usually larger geting additional reduction) that has a hub on the outside.
So, what does this mean in English? The axles (and by extension, diff) get mounted higher in a portal than in a standard axle. You get more ground clearance, and usually some killer gears. Unimog axles are the best known, although Volvo has a few that are lighter.
Dad's harvester tractor back home has a goofy portal axle setup; he bought it in 1967.