what if i bought it second hand

Then you ask the seller to remove it or give you a refund, or if applicable, ask the people who run the site or store you bought it through for a refund. It's an anti-theft measure.

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Hello ~ If I may add…. if you cannot get the seller to unlock it or refund your purchase recycle it responsibly for we cannot help unlock it and neither will Apple . Take a look here:

Activation Lock for iPhone, iPad, and iPod touch - Apple Support

Also:

The All Too Common SAD Reality of Buying a Used iPad/iPhone

~Katana-San~