The Powermatic PJ-882HH is an 8-inch jointer with helical head cutters and a parallelogram base. It is nearly identical to the Powermatic PJ882, which only has standard straight blades.
The standard model, the PJ882 only has 3 standard knives, and they even lack the quick-set feature found on some cheaper Powermatic jointers. This makes the helical head of the PJ-882HH a big upgrade. The helical head cutters are quieter, last longer, are easier to replace, and are better at dealing with difficult grain patterns.
The only downside of the PJ-882HH over the PJ882 is that the rabbeting ledge cannot be used with the helical head cutters. So if rabbeting on the jointer is an essential operation for you, stick with the normal PJ882.
Powermatic also offers (cheaper) 8-inch jointers with a dovetailed base, rather than the parallelogram base found on the PJ-882HH. Parallelogram bed jointers make it easier to change the height of the tables and are less prone to sagging and wear.
Additionally, Powermatic’s parallelogram jointers also have longer tables, and a longer and heavier base, making them better a clear upgrade compared to the dovetailed wedge-bed jointers (the Powermatic 60C and 60HH).