Perhaps you refer to the Assistive Touch feature - described here:
Use AssistiveTouch on your iPhone, iPad, or iPod touch - Apple Support
It is a common misconception that an iPad (or iPhone) can remain fully functional with damaged or defective physical buttons.
Whilst Accessibility features (such as assistive touch) can be used to augment the User Interface, these features cannot be used as a substitute for physical button sequences that must be used to trigger system recovery actions. Sooner or later, you will encounter a situation from which you cannot recover.
Should you need to do so, should you have any un-repaired physical button, you will not be able to perform a forced-restart of your ipad, resolve a locked-out (disabled) iPad - or reset a forgotten device passcode.