When you invite Friends or Share Groups to your meeting, you have the choice to make their attendance to the meeting optional or required. If you make the meeting optional, you invitees will have the option of RSVP’ing either yes or no. If you make the meeting required, then there will be no RSVP button in the Meeting invitation email that they receive.
To see the invitation status of the people you invited to your meeting, all you need to do is click on the blue “Attendees” link next to your Meeting in your calendar. If there is a gray “Invited” button, this means your invitees have not responded to your optional meeting invitation. If there is a blue “Required” button, it means that you have made the attendance of your invitees mandatory. If there is a green “Accepted” button then your invitee has agreed to come to your meeting. If there is a red “Declined” button, then your invitee has refused.
If you no longer want a person that you invited to come to your Meeting, you can un-invite that person. You also have the option of re-sending the Meeting invitation if one of your invitees hasn't responded to your invite. You can perform both of these actions when you click on the invitation status box to the right of the invitee's name. Please see the image below:
If you do decide to remove someone from your "Meeting Invite” list or to re-invite someone, be sure that you click on the green “Save” button at the bottom of your Meeting invitee list after you have selected one of these options.