When you need to monitor the latest work and task progress for a given workspace from one place, with help comes an additional "Dashboard" view, which you can configure according to your needs. There you can see the new files that have appeared in your inbox, the tasks you should take care of first, the progress of relization of selected projects, or the log of recent activity in the workspace. The last one will also allow you to record your own entries in the activity log, and view it also for a specific date (if you needed to see what you were working on that day).
Dashboard is a special view that you can customize, you can configure widgets on it, which will allow you to get quickly to the most interesting summaries related to a particular workspace. If you are interested in the number of documents in the repository, or your recent activity - you can check it here.
In Activity Feed you can see your recent activities in a given workspace. They can be about changes in documents or tasks. If you want to log your own information there - also no problem. The tool is great when, for example, you want to report to someone about the work you did on a project on a given day.