When the screen orientation changes the system will, by default, destroy the current activity and create a new one while preserving its state

I can not able to understand this sentence in android documention. Since it is saying

When the screen orientation changes the system will, by default, destroy the c开发者_运维问答urrent activity.

and it also saying

create a new one while preserving its state.

but actully it is contrary. How could it be? Can anybody explan to me.

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Refer this Retaining an Object During a Configuration Change
And Activity restart on rotation Android where it discussed in detail