The Recycle Bin is where the photographs that are culled are place. It is similar to the recycle bin or trash bin for the operating system.
The Recycle Bin is holds only those files culled from the current directory.
Each directory has its own Recycle Bin. When you select a different directory, it will have a different Recycle Bin.
Note that placing a photograph in the Recycle Bin does not delete it from the hard drive.
You can restore culled files from the Recycle Bin to the Thumbnail View with these buttons

You can delete the all the files in Recycle Bin from the hard disk by selecting this button

When you delete a photograph from the Recycle Bin, it deletes the file from the hard-disk by moving to the operating system’s recycle bin/trash. You can still recover the file by restoring in from the operating system’s recycle bin/trash.