Segmentations are the key-entity in VIAN (and most other Annotation Applications anyway). Each Segmentation created in VIAN, is shown in the Outliner in the Segmentation category. Essentially a Segmentation consists of [0, … , n] Segments, where each Segment has a Name, ID and a Annotation Body, this is, an piece of text describing the Segment.
One Segmentation in a VIAN project is always referred to as the Main Segmentation, this is the one currently used for sorting the Screenshots. How to change the current Main Segmentation is explained in Changing the Main Segmentation.
Screenshots are automatically ordered and reordered according to the Main Segmentation.