What is an ENT Doctor? My Physician wants to send me to one? Please help!?

I am 20 and I had found a lump/ swollen painless lymph node on the left side of my neck 4 months ago and went to the doctor this week Monday. My doc put me on a course of antibiotics, Doc took blood test on Monday, I got a chest X-ray Tuesday waiting for results, and doctor wants to see me back in 2 weeks to check lump on the left side of my neck. Plus I came down with a cold or flu or whatever that is now causing me to cough, have a congested nose, sneeze, and a sore throat the same day I went to doctor to check 4 mon. lump in my neck which is smaller than a dime. Anyway My doctor said if the lump doesn't go away he's going to send me to an ENT doctor to get a biopsy. Is an ENT doctor an oncologist? What does an ENT doctor do? What should I expect from an ENT doctor IF i have to go to one in case my lymph node doesn't go down?