prestel databases is commonly referred to as the 'tree structure'. the structure is shown pictorially as an inverted tree with the data considered as 'leaves' of the tree, accessed via 'branches' which serve as a means of classifying the information. there exists quite a lot of jargon regarding such structures but in order to appreciate the concept it is necessary to mention just the node, page and frame. nodes are the junction pages in the tree at which a number of choices can be made leading to other nodes or to the information itself. pages are the final levels in the tree and contain the actual data-these may be divided into frames which are really screenfuls of information.