I need help red smooth patch on tongue, what is this?

Likely glossitis. : Most likely a 'red circle' on the tongue is a variant of normal anatomy, a benign inflammatory condition called glossitis, or an inflammatory lesion called geographic tongue. It happens in response to trauma, viral or bacterial infection, or irritation (some spices). Either way, you should seek a consult to be sure. Until then, treat it as an std and be responsible to your sexual partners.

Red Smooth Patch: My best guess would be something called geographic tongue. I said a "guess". While you could "google" it and see if the adjacent photo looks like what you have, we can't diagnose these things over the internet (nor should you!). If you are smart, you will visit your dentist for a definitive diagnosis. Then your own dentist can discuss whatever you need to know about your condition.