I'm 18 years old and I have a tooth in the back of my upper left side thats growing out of my gum. Is that normal?

Possibly. It is normal, at yout age, to have a wisdom tooth erupt and expose itself.. See your dentist for an x-ray confirmation.
No. A tooth growing out of the side of your gums instead of the normal position is not normal. Based on your age, the tooth could be a wisdom tooth that may be require removal.