Hi Surreyfrog

You are completely right in saying that "they both would describe things that are done by a business". This is the essense of the matter. Just keep in mind that an enterprise carries out functions (sales, purchases, manufacturing etc), which contain business processes (the famous term "business process re-engineering" was exactly about these!). The buisness processes contain tasks - the lowest level of user's activity in a process. The activity is purely a set of small steps to complete the tasks. Having this hierarchy in mind, add additional attributes like actors, business docs and business data to get the whole picture about the current business state. Having collected this information, move to describing the target state with the same pattern in mind!

Don't get lost now!