Using Javascript parseInt() and a Radix Parameter

Question

Can anyone explain how the parseInt() functions works and what the Radix Parameter is?

As a case study, I am trying to get to grips

Answer 1

In the ECMA Script 5 when the string starts with 0 and no radix is specified the default behavior is decimal (as opposed to the earlier versions in which it was octal)

Source: parseInt() on Mozilla Developer Network