WD backup how backups work

Legacy Products WD Backup
1

I am using WD backup on my passport hard drive. after the initial full backup, does the software just backup any file changes or relocation of file only?

2

Hello,

Please refer to the following KBA article: Error

3

So i have noticed it after a file has changed only the latest version of the file is there. is that how it works? not a history of file copies?