Topics are used on the VLE to give a coarse granularity to the organisation of modules, in a way that should make sense to the student. For example the Media Files topic is self-explanatory as far as its scope is concerned. The current contents being Images (A), Images (B), Images (C) and Other Files (B), the "other files" lesson covers sound and video, and as things stand in less depth than images. If things change in future, with more video lessons, the Topic remains the same.
Clearly it may make sense to say that the course evolves on the VLE while the Topic here may remain the same. Topics here have footer templates that go on related pages.