I’m a total beginner to the game, for forgive me if I am asking a stupid question. If you fail the courage test when trying to charge a model with the terrifying special rule, is the model that attempted the charge taken off the board as a casualty? Or does he just fail to charge? Thanks.

He fails to charge and stand doing nothing for the rest of the turn (moving again, or firing an arrow). He will fight and wound if he is charged but that's it.

Actually that has been FAQ'ed....see below from Official FAQ's from Hobbit Rules. Can be found on Warhammer Community FAQ section...Models who fail courage tests can still shoot or spear support, as well as fight normally if they are charged.

From FAQ:
Q: Can a model who has failed a Courage test to charge a terrifying enemy do anything further that round other than fight in combat if charged, e.g., shoot or provide spear support to a friendly model? (pg 83)
A: Yes.

_________________
T'was in the darkest depths of Mordor, I met a girl so fair..
But Gollum, and the evil one crept up and slipped away with her..