What is the purpose of repositioning characters in ff4?

I just want to know why you need to change positions of people in ff4. Im thinking it has to deal with exp. points but am I right?

The people in the back are more protected. Put tanks like Cecil and Kain in front while keep frailer members like Rosa or Rydia in the back.

The purpose in reposition has to do with attack and defense. Where they are positioned determines how much damage they can deal(with melee weapons) and how much damage they will take. So positioning becomes important in strategy: you definitely don't want a caster with low health and weak armor in the front row.

Basically it's fighters in front, casters in back.

Characters in the back take less damage, and deal less physical damage.

Also, for some bosses you can reposition your characters so that when the boss ambushes you the tanks end up in front anyways.

As stated, there's a front line and back line.

Those in front can deal more physical damage, and take more.

Those in back deal less, take less.

Main purpose is to typically keep your stronger melee characters out in front, and mages/support in the back.

And as mentioned, some boss fights mess with your order, while back-attacks also leave your orientation swapped, so flipping order mid-fight becomes necessary then.