For example, "formatting windows 10" would not be the most correct way to express what formatting is. The correct way would be to say "format hard disk", "format memory unit", "format usb memory", etc.
But when we refer to "how to format windows 10" we really mean how to format the partition our operating system occupies on the hard drive. Also to the subsequent installation of a new copy of windows in the formatted part.
And formatting that at first what comes to mind is to delete, clean, ... more than this is to give a format to the memory unit that we are handling so that it creates a file system with which you can operate in our operating system.
So even if you have formatted a hard disk partition it does not mean that old data from previous installations cannot be recovered. That's why more than deleting, it's formatting. If you want to format a hard disk at a low level, i.e. a deep deletion of everything that has been installed over the lifetime of a hard disk, then we would already be talking about a low level format. This way, nothing could be recovered from that hard disk. So I will talk to you about Darik's Boot and Nuke - DBAN tool some other time. By the way, there is also a way to format Windows 10 without an external copy. You can see it here in this post.