Auditioning and Nervous!!?

I'm going to this performing arts camp and we have to audition, its not that big of a deal but I have no idea what to expect, I mean I've auditioned before but they've provided all the music. So what type of songs would be appropriate for my age, I'm 14, it has to be a musical theatre song and no more than 2 minutes. Also I have to do a monologue....what the heck is that?? And do I have to make it up?? And any tips on how to not be so nervous?? I'm so scared and I don't wanna do this...HELP!! PLEASE!!! :) Thanksss