Actually Inf returns the IEEE arithmetic representation for positive infinity.
Infinity results from operations like division by zero and overflow, which lead to results too large to represent as conventional floating-point values. An attempt to divide a floating point number by zero will lead to +-infinity by the IEEE 754 floating point standard
while NaN returns the IEEE arithmetic representation for Not-a-Number (NaN). These result from operations which have undefined numerical results. The IEEE floating-point standard, supported by almost all modern floating-point units, specifies that every floating point arithmetic operation, including division by zero, has a well-defined result.