"Enable OS Integration" is a Windows-only setting found in Preferences - General. It is enabled by default and provides right-click access to the SpiderOak backup product in the Windows file explorer. Due to differences in how file managers are implemented in other operating systems, there is no corresponding setting for Mac or Linux.
This option normally works well, but you are welcome to disable it if desired. Under some circumstances, having this option enabled might be associated with causing Windows to launch the backup application in an apparently random manner, or for the backup GUI to be slow to respond. If you have either of those problems, disabling this setting may help.