just wondering what a tantrum is and is it hard to do?

backflip like you would do on a trampoline and no

A tripflipped, backflip. No.

is a frontflip easier?

my turn, <BR> <BR>no

What's the difference between a tantrum and a heelside backroll?

If you look on the home page, to the left, there is an instructionals link that has videos of many of the tricks and you can see the difference

back roll is more of a cartwheel (tip or tip) and a tantrum is more of a flip (edge over edge)

You can also just type in "tantrum" or "wakeboarding backroll" or something into google or youtube.com and you'll be able to see different examples.