When logging into your database, the default login page is your Today's Overview page (which is otherwise accessible under Dashboard --> Today's Overview, or by just clicking on Dashboard):
There are several components to this page. Here we'll take a look at the Contacts by . . . component on the right-hand side of the page:
This provides you a pie chart representation of the contacts in your database, either by Category, Source or Status. To flip between the views, click the Change option in the top right corner and you'll see the below:
In the example below, we have selected the Contacts by Category chart:
Each slice of the pie represents the contacts within your database that have been assigned a particular Category. If you hover your cursor over a slice, you might see the following:
In the above example, I hovered over the slice of the pie chart representing all contacts assigned a Category of "C Client." Doing so provides you with the Category name, the number of contacts assigned that Category and the percentage of your database contacts that share that Category.
Clicking a slice will take you to a filtered version of the report, displaying those contacts only. In the example above, clicking the slice would take you to the Contacts by Category report, displaying only those contacts Categorized as C Clients.
Note as well that below the chart you have a key indicating what Status, Category or Source each color represents.
As a final note, you can add, edit or delete your Categories, Sources and Statuses under Manage Your Account —> Manage Database Lists.