Delete backups on computer

I apologise if I have placed this in the wrong area, it is regarding Time Machine backups on my computer and I was unsure whiich community to put it under.

I am wanting to delete unwanted files form my computer and have aleady got rid of a lot of files. But when I went to the 'Apple' logo, 'About This Mac', click on 'More Info...' then 'Storage' it says I have over 200gb in back up. I thought backups go to my 'Time Machine' when I connect me external harddrive I have for my backups but it appears to save some backups on the computer. From what I can see it has saved the past four days on my computer.

Is there a way to remove these backups or change the settings to only save on my external harddrive?

Thank you for your time.