Images are grouped in three ways:
singles: these are stand alone images that are not part of any collection.
collections: this is a group of images that are connected thematically and generally delimited by time, where an image from a later period would be incongruent. These collections will not be added to.
galleries: a group of images that are thematically connected, but unlike collections, time is not a constraint. Galleries can be added to and when they are their publishing date will reflect this.