Delete Time Machine backups on Macintosh (Internal hard drive)

Hi,

I made a Time Machine backup on external hard drive. Later, when I went to restore back from Time Machine backup (Command+R), there were two options to select from i.e. restore backup from external hard drive or restore from Macintosh (Internal hard drive). It makes sense to restore from external hard drive because I took Time Machine backup there. But when clicked on Macintosh (Internal hard drive), it was also showing some backup files where I had the option to restore form.

I have two questions. Firstly, how the Time Machine made backup to Macintosh (Internal hard drive)? - whereas I did not take any backup on internal hard drive. Secondly, how to delete such backup files from Macintosh (Internal hard drive)?

Thanks,

Adnan Arshad.