When you send a Planner invite, you can restrict the invitee's permissions, so that they can only access certain parts of your First2Care system. For example, you may want someone to help with your plan/pre-plan, but not with your schedule. To do this, you will use the Permissions section on the My Invitations page. This will be just under the main Create an invitation section.
By default, an invitation gives Full Access. You can, however, change it to Custom Access to restrict permissions. This will cause more options to appear, which you can set individually.
Each permission has the option of Full or No Access to that particular feature. Descriptions for what each feature controls are listed next to them. Of particular note is Connections & Invitations. This will allow the invitee to invite more people on your behalf.