Here's how we arrive at this name:

* Pt: Platinum

* (PO3): Phosphite ion (PO3)3-

* 3: Indicates three platinum atoms

* 4: Indicates four phosphite ions

* (II): The Roman numeral "II" indicates that platinum has a +2 oxidation state.

* tetrakis: A prefix meaning "four" used for complex ions

Since the compound is neutral, the total positive charge from the platinum ions must be equal to the total negative charge from the phosphite ions.