Do N. Online Backup and N.360 Backup "edit" what they save?

I'm starting over with a new computer after transferring everything from an old one, which caused duplication of files and folders.  Causes me to wonder what protocol is used by the backups.  When a file that has been changed is saved to backup does it overlay and replace a version of the file previously saved or is one with the new changes also saved?  If I edit my MY PICTURES folder, deleting some pictures, when the folder is next backed up, will it contain the pictures I deleted or not?  Ditto MY DOCUMENTS?