What does it mean when you have a really sore throat, stuffy & runny nose, and swollen glands under your jaw?

You are sick. Sorry to be blunt, it sounds like you have a bad viral infection, flu or cold. It is also possible you could have tonsillitis or pharyngitis leading to swelling of your lymph nodes.
Upper respiratory. This may be a banal viral upper respiratory infection. Usually it starts subsiding within 2-3 days. If it persists, especially fever, you want to see a doctor. If you have any risk factors for a more serious disease (unusual sex practices, use of i/v drugs etc.) you may want to have these symptoms checked out by a physician promptly.
Many possibilities. You cold have a simple viral infection. You could have a sifnificant bacterial infection, you could have a rare fungal infection. Generally the lymph nodes in the neck will swell with viral and bacterial infections. You describe a classic viral infection. Strep throat is not usually associated with runny nose. If there is fever, difficulty swallowing or you believe you are too ill, see pcp.