The Configure User Roles page allows you create new roles for your users and assign tasks to these roles.

Access this page by going to Site Configuration → Security Configuration → Configure User Roles.

This page contains a list of the roles set up for your group, with descriptions of what each one does.  The default roles are usually sufficient for most groups' needs.

Clicking the Assign Tasks or Add a New Item buttons will open up an individual record, as shown below.

Here you can choose the name of the role, its description, and which Authorized Tasks are enabled for it.

Each Authorized Task has a corresponding Task Description, indicating what type of access that task provides.

Clicking the check box to the left of a task will enable it for the role you are editing.

To assign an individual task to many roles at the same time, see Assign Tasks To Roles.  To see a breakdown of your site's roles that lists what tasks are enabled for each, use the Role Task Report.