Yeah, Monster Hunter Freedom Unite was probably also the game I spent most time on my PSP.

It depends on what games you like, but I loved Persona 3 Portable and Kingdom Hearts Birth by Sleep.
If you liked Monster Hunter, you could also try God Eater. It is a really gold Monster Hunter Like with a good story!

It’s basically short for “Ferromagnetism”. So your guess with that is right. You can check the Wikipedia article about that topic, it explains quite well. I currently don’t have much time to give an ELI5. :(