Does lost mode with find my iphone require the thief to enter the phones passcode or your Apple ID?

I had a simple passcode on my iphone and I know that's bad but I'm wondering if they just have to guess my passcode or do they need my apple id password to get it out off lost mode?

They can't get it out of lost mode, they need your apple ID/Pwd and also can't wipe and setup the phone without it