When you are creating a Time Entry you will be prompted to specify a Role and Task Type.
The Role is specific job role capacity you are acting when completing the work. This is not always the same as your primary job function. For instance, while you might be an Owner, the role you are facilitating for this time entry might be that of an Admin.
Next, the Task Type is what activity you are recording your time specifically against in the role you have chosen. For example, your might be holding a client meeting so your Task Type would be Meetings. However, you might be doing that in the Role of a Client Manager. Task Type is required if the time spent needs to be tracked as billable or not billable.
Specifying the Role and Task Type are important because they ensure the right dollar amount is associated to the time entry that is made.