**Next Page Path has been deprecated (Retired)- Use Page instead.**
The Second Page will always be the second page browsed in a session, while the Next Page Path will depend on which page you are setting on the Previous Page Path.
For example, a user visits your site on Page A and then moves to Page B, and then to Page C and last page D.
If you select as Previous Page Path: Page A, then Second Page and Next Page Path will be the same: Page B.
But if you select Page C as the Previous Page Path, the Second Page will still be Page B, while the Next Page Path will be Page D.