There's no dumb questions, only dumb people who don't ask questions!
ICU you'll have usually a 1 nurse to 2 to 3 ratio, they'll be sicker, often w/ vasoactive drips, ventilators, frequent monitoring, etc. Acute care you'll have a higher patient load, less frequent vitals, pts (hopefully) not as sick.
Both areas have their challenges and rewards. Generally to work in an ICU you have to have more certifications such as Advanced Life support, Trauma Nurse certification, etc.
I just tried to give a brief overview. I'm sure others can add more info.