Use the "Contacts" tab to see your Contacts in details
It allows you to build a customized classification of your Contacts.
You can also manage your Companies within this tab.
To see the list of Contacts of one Category, just click on Category you are looking for, in the panel (up-left)
The list of Contacts of this Category will appear in down-left of the screen.
You can Add new Categories or modify existing ones using the left panel, as shown here