This format is used for storing bitmap images with improved levels of color and brightness performance. It combines exposures to record darker tones in the shadows or detail in the lighter areas of a given photo. HDR is able to combine multiple images with different levels of light distribution. It is used to create rich images.
This format is a vector images file in the Sketch Drawing program, which serves to edit and create interface designs, applications and software shells. SK-files contain objects and layers which can be edited independently of each other.