TOPIC: Agile - iterative & incremental life cycle

While reading the 1st chapter of PMBOK 6, I came across agile methodology & its types like iterative & incremental. I would like to understand the difference between iterative & incremental life cycle as they are mentioned in brief in PMBOK 6.
To my best of understanding, in iterative LC, the entire scope at higher level is known during the initiation of the project which is further known in detail using progressive elaboration in the subsequent phases . The product development takes places through series of iterations . In increment LC, the product is development take place through series of increments where during each phase some features are developed & goes on till all features are incorporated. I would like to know whether the entire scope is known during the initial phase or known partially & the remaining scope is known during the subsequent phase .