Why are there 2 salary fields when posting a job?

There is one field for providing minimum and maximum salary, which shows up only on the full page, whereas the Salary on offer field shows up in the posted job listing and can then be searched by the candidate. Both need to be filled in for maximum coverage.

Likewise with a candidate, there is one field for salary and one field for requested salary. The first field is for your current salary, whereas the second one is the requested salary for a candidate when considering a move.