There is one contact list for your entire organization.
When you add or edit contacts, you add or edit them for everyone in your organization.
While it is possible to manually add contacts, the contacts you need will likely be added automatically. Similarly, the contacts you use will be added to the project team automatically.
There are 3 components to contacts: a person belongs to an organization. An organization can have locations, and each person can be assigned to one of the locations. Therefore to associate a location (ie. an address) with a person, first add it to the organization, and then choose that location for the person.
TonicDM automatically adds hint icons to contacts: Bounced, Home Address, Robot, Misspelled, Rejected, and Spam Complaint. Read the details here.