In Contact information view you have the possibility to manage customer's contact information like addresses and contact persons. When you create a new customer and add address to it, that address will also be assigned as the headquarters of the customer. Some of the financial integrations require that the headquarter address is given so always check that this address is correct.
If you add more than one address to customer and want to edit the headquarter at a later time, you can do that using the "Change" link shown on the existing headquarter.
Activities section lists all activities linked to customer (to-dos, calendar entries and project tasks) dividing them to planned (on-going) and past activities (done). You'll have easy access to any activity from this list. In this view you can also create new activities.
Managing customer details like VAT number and Industry is done in Contact information view. You'll also see all market segments selected for the customer.