Hi, I Have Been Prescribed Nitrofurantoin For A UTI But

Hi, I have been prescribed Nitrofurantoin for a UTI but wasn't given much information on the phone when my doctor called me. I was wondering what type of infection this drug is commonly prescribed for, and also if it is normal for the symptoms to worsen in the first day or two of treatment? I am concerned as I am a 20 year old male and I know this infection is uncommon for my bracket. Thank you.