Creation of.bak files

I am new to CM. I have noticed that if I open a file and modify/resave, it automatically creates a .bak file, and will continue to add more .bak files over and over each time I modify the original file. Why is this and can it be disabled? Why would I want so many .bak files piling up?

Cryptomator does not create bak files.
I guess an other software creates this.
Maybe a backup tool? Or some sort of versioning tool?

You are correct MIchael. The software I am using (Open source version of Microsoft Office) was configured as a default to automatically create a backup file. Once unchecked. It no longer creates the .bak file. Thanks!