LOFT is a line flight in the sim. Usually, you fly one leg where everything is "normal" then one leg where all hell breaks loose. They grade you on how you deal with it.

LOFT tends to be more for captains because a lot of it involves judgment and cockpit management. As the FO, just be sure you know your memory items and do what you are told. Chiming in if the skipper tries to do something dumb is a bonus.

In a LOFT you really aren't in jeopardy unless you don't know how to fly, do something incredibly dumb, can't run a checklist, or don't know your memory items. Everything else is a debrief. They tend to be much lower key than a PC which is an actual checkride.