By default - all conferences will be recorded 
These will be deleted immediately after the call is completed , unless moderator chooses to retain the recording. 

There are lot of Purposes for recording the call. For Ex: 
To charge the minutes 
To record the meeting minutes . etc... 

Moderator can select an option to retain the recording and he is the only person will listen that , call will be recorded. That is the feature of Moderator.