Can the time machine backup & omit duplicate items on your macbook air, in order to save space on your external hard drive?

Hi all!

I'm new to MAC but will never go back!

I'm finding the "backup"/time machine feature great in some ways but also redundant in others. LIke with PC you can choose what you want to save on your external hard drive so that you maximize the space on it. With Mac, the backup is done fast & easy but since it saves your data "as is" your desktop & macbook on any given day, it's going to continue to save files that you haven't deleted on your macbook air that you want to continue to view or work on; as opposed to recognizing that these items are duplicate items, so don't save again on the external drive!?

Did I understand correctly or is there an option for the Mac to recognize these items & omit them during a back up? I know you can manually go & click on specific items for the back up Not to save but this would require so much time! I figure Mac is so ingenious, it Must have a feature that already does this: recognize duplicate items & Not back them up every time?! No?

Please help this Mac newbie!! Thanks so much in advance!