Thank you for this feedback!
The F and C stand for Food and Cost, they indicate how much food will be consumed each turn and what the initial cost is to add a party member. I will update the description to make this clearer!
At the moment the only difference between the classes is the amount of initial life and food consumed. I intended to implement a basic rock-paper-scissor battle component, but I ran out of time in the gamejam; I will be adding this in the future!