Help with 2 spells

Hi. I need help with the Passive mana shield spell and the spell that tosses units around.

Can someone explain the underlying principle beneath the two spells mentioned?

For Passive mana shield: How do you retrieve the damage a unit has taken? I don't read JASS and have no idea what the trigger says. I need an explanation in as little JASS as possible how it works.

For the Knockback spells: How does one set a unit's flying height? As far as I know it only applies to flying units how did you manage to get it to work for non-flyers too?

Any help with this is really appreciated. Thanks.