The notation "G: Y → Z" represents a function named G that maps elements from set Y to set Z. In this context, for every element in Y, there is a corresponding element in Z determined by the function G. This means that G takes an input from Y and produces an output in Z. Functions like G are fundamental in mathematics and are used to describe relationships between different sets. The arrow (→) indicates the direction of the mapping, showing that Y is the domain (input set) and Z is the codomain (output set).