A lock screen is essentially a simplified login screen found both on Windows and Mac. This lock screen appears every time you turn on your computer or wake it from sleep, prompting you to enter your passcode. Although it's main function is to serve as a login screen, it can be customized just like your desktop background and be modified to add helpful widgets such as the weather or recent emails to view at a glance. 

How To Change Lock Screen On Mac?

Navigate to System Settings > Lock screen."

How To Change Lock Screen On Windows 10/11?

Navigate to Start > Settings > Personalization > Lock screen.