Starting from iOS 8, any deleted photos or videos from the Camera Roll will be transferred over to a new folder called Recently Deleted. This new album was added to store deleted media files on your iPhone or iPad for 30 days and it will then remove permanently after that.
For some people, this might be a useful feature because you can easily restore a deleted photo just in case of a mistake. However, most iOS users found Recently Deleted to be an annoying feature because they have to get rid of their photos and videos twice. Not to mention that the data will continue to be counted, which means your storage will stays the same as is.