The Notes tab allows you to provide additional text description for some task types. Note you create are sent with meeting invitations - agenda style, plain text.
Notes can also be included in invoices.
Notes also can have security associated with them. The levels of security are defined by the levels you have set for the functioning groups in your organization. For example:
These descriptions for ‘Security1, Security2, Security3, etc.’ can all be changed. Who should be able to see/know about this task. It’s a way to restrict to only having certain departments access to the data.
Notes can be included on invoices. For example, you can allocate a ‘cost’ for this task. These notes may help justify the reasoning for the ‘cost’.