A hard reset is a process of reverting a device back to the state it was in when shipped from the factory. That is to say, it erases all data including apps, user profiles, and settings. Hard resets can be helpful for wiping all data before selling a computer, smartphone, or tablet. Also, they are useful when you have an operating system error that you cannot fix.
Smartphone hard reset: With a smartphone, a hard reset restores the smartphone back to the original operating system and apps. A hard reset erases all user data and any apps installed by the user.
PC or laptop hard reset: When it comes to a computer, a hard reset is performed by reformatting your machine and reinstalling its operating system.