Low Power controllers
The power consumed by an application/device can be divided in aspects:

a) the power needed to do the required amount of computation

b) the power required by the chip in its lowest power mode (sleep, deep sleep, hibernation, etc.)

c) the power required by the chip while doing the barest minimum of activities

Depending on the application, one or more of these aspects will dominate the overall power consumption. Low power chips generally have a very low power mode, reducing the power for aspect b), and ways to have the hardware take care of c) (responding to keypress, timeout, A/D conversion completed, etc.) without involving the CPU (thus reducing power).

Low Power or Ultra Low Power are just marketing terms without any agreed-upon kwantitative meaning. A manufacturer has to come up with a new term for the chips that do better than its previous range of Low Power chips... But an engineer doesn't care about the name. The datasheet (and often info beyond that) is what realy counts.