At any given time, a firm has a slew of work being performed by many different people assuming many different roles. Within those jobs, many individual activities are being completed to ensure the client is served. These activities may or may not be billed for, and when billed, charged at differing rates depending on who completes the work. As the work is completed, time is logged against these activities to ensure fixed fees are profitable for the firm, while for time and materials engagements, client-based activity is billed back to the client.
To track which of these activities is billable, and to associate the right billing rate, you need to update your Task Types to suit your firm's needs, and make sure each time entry is assigned a Task Type.
A Task Type is what you record your time against, indicating the type of activity you are doing within the Role you have chosen. By also adding a Task Type to specific tasks in your work items and work templates, you can also get more granular reporting on actual time spent versus your budgeted time for that type.
Note: if a Task Type is set to "none" the default billing rate is $0, unless you set a custom rate within that specific work item.