The Recycle Bin becomes a very important component of Microsoft SharePoint Online when you delete an object from you environment. The Deleted object is moved into one of the two Recycle Bins from which it can be safely recovered.
When a user deletes an object on their SharePoint Online site, it moves into the first stage Recycle Bin or the user’s Recycle Bin. If the user has Contribute, Design, or Full Control Permission, the deleted object is available to the user and it can be accessed from the “Recycle Bin” link on the Quick Launch Bar. The deleted object stays in first stage Recycle Bin until it is purged by user with appropriate permissions, or it is automatically deleted after 30 days.
If a user deletes an object from the first stage Recycle Bin, the object moves to the second stage Recycle Bin or the Site Collection Level Recycle Bin. If the User restores the object from the first stage Recycle Bin, the object is restored to its original location.
When an object gets into second stage Recycle Bin, it is available to users who have Site Collection Administrators role and can be accessed from the Site Collection Administration section, Site Setting page. Deleted objects stay in the second stage Recycle Bin until a site collection administrator deletes it - or it’s automatically deleted after a number of days (up to 30). Any object can be permanently deleted after second stage Recycle Bin - or they can be restored in this stage by site collection administrator to its original location.