You appear to be encountering the Activation Lock for iPhone, iPad, and iPod touch - Apple Support feature, related to iCloud - Find My - Apple . Activation Lock is designed to prevent anyone else from using an iPhone, iPad, or iPod touch if it's ever lost or stolen. Deactivation requires knowing the Apple ID and password that set the feature, or by placing a special request to Apple to reset the device. This Apple ID information essentially defines the current ownership of the device.
Click on this link to learn how to remove Activation Lock --> How to remove Activation Lock - Apple Support
If you do not know the required information and you are not the owner, get the owner of the account to remove the lock (the section: "If you no longer have your iPhone or iPad" in: What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support ), or return the device for a refund, or recycle the device. The device is otherwise useless to you. If the owner is unknown and has not provided contact information as a message showing in the login screen, there is no way to contact the owner unless the person who gave you the device knows them.
