what is deadlocking?

Using the Key in the Door Lock Cylinder, you can turn it through the "Lock" position and onto the "Deadbolt" position. You can only deadbolt the car's doors with the key. Using the Keyless Entry Remote will not deadbolt the doors. Neither will the power lock/unlock buttons inside the car.

If you deadbolt the doors with the key, you can only unlock the doors with the key. In other words, if you deadbolt the doors with the key, you will not be able to use the Keyless Entry System to unlock the doors.

Hope that's clear.