You will see a yellow checkmark next to your appointment in GoReminders if your client has confirmed, a red exclamation mark if they need to reschedule, and a black exclamation mark if they cancel.
You can have these notices sent to your staff members via email or text message through the settings on the Staff profile.
You can also be notified when there is a reply. Go to the Reminder settings page to choose if you'd like to be notified by text or email. Just look for the Notifications section near the bottom of the page.