On the right-hand side of the ribbon you will find the icon for the contextualised activity journal.
If you expand this by clicking on it ("expand"), activities from the last month are displayed that are related to the object selected in the open form.
This is clearly illustrated by the example of contacts: even from the overview, the activities relating to the selected contact from the past month are displayed when you go through the contacts, without you having to explicitly open the contact.
This function is also very useful to get a quick overview of what has happened in the last month, e.g. with projects or incoming invoices.