Region features are stacks of filters that can be used to create new region-based classifiers in Dragonfly's Segmentation Trainer. The features extracted from regions are the different metrics that represent the region itself. For example, the histograms of the intensities of the pixels in the given region. Downloaded region features will be available in the Feature panel of the Segmentation Trainer. See Region Features for more information.
You should note that the Infinite Toolbox also includes a selection of Dataset Features, which can be used to create new pixel-based or region-based classifiers.