If you have an iCloud account, a Microsoft Exchange account, or a supported CalDAV account, you can send and receive meeting invitations.
Invite others to an event. Tap an event, tap Edit, then tap Invitees. Type names, or tap to pick people from Contacts.
RSVP. Tap an event you’ve been invited to, or tap Inbox and tap an invitation. If you add comments (which may not be available for all calendars), your comments can be seen by the organizer but not by other attendees. To see events you’ve declined, tap Calendars, then turn on Show Declined Events.
Schedule a meeting without blocking your schedule. Tap the event, then tap Availability and tap “free.” Or if it’s an event you created, tap “Show As” and tap “free.” The event stays on your calendar, but it doesn’t appear as busy to others who send you invitations.