Inward tasks are when you can switch off all means of communication - email, phone etc.. and focus on the tasks at hand that require no other input besides your own. Outward task require external communication (e.g. getting back to people on the phone, over email, meetings, calling clients etc...)
If on daily tasks you could split these tasks - grouping them, you would be much more productive when attacking the day. Inwards tasks first followed by outward or vice versa.