Complex sentence: The Sikhs practice both the quiet individual recitation of "Naam" in ones mind, commonly called "Naam Simran", and the loud and communal recitation of "Naam", called "Naam Jaap".
Split into simpler sentences: The Sikhs practice both the quiet individual recitation of Naam in ones mind. This is commonly called Naam "Simran" while the loud and communal recitation of Naam is called "Naam Jaap".