By default, hosts (+ any admins) will receive automatic notifications of:
New submissions to the event
Changes to existing submissions to the event
These notifications will go to the email associated with the account.
The host can toggle on or off this setting on the account and event-level by going to:
My Account > Notifications
Notifications are controlled both on the event level and on the level of the account itself. You can choose to receive updates from some events but not others or to disable these notifications entirely. There is also the option to disable notifications for some actions and enable them for others, so you could potentially receive notifications for new registrations, but choose not to receive them for edited ones.
Any collaborators with access to the event will also receive these notifications.