Provide me with explanation for given snippet, ensure the explaination is clear, concise and readable.
The given snippet is a hierarchical structure representing a transition group containing a pair of transition images for a sidebar. The transition group contains two sub-elements: "view-transition-old" and "view-transition-new," which likely represent the old and new states of the sidebar, respectively. This structure is used to manage and represent the transition animation between the old and new states of the sidebar in a user interface.