I started to answer, but Mayo Clinic has an article that explains it all. I'm not sure if links are permitted, and I tried to find a non-link way to get you to the page but was unable to.

They state that Afib and Atrial Flutter are Tachycardias. Also discussed is Supraventricular Tachycardia and Ventricular Tachycardia. 

SVT (Supra Ventricular Tachycardia) occurs from a point above the Ventricles (supra means above).

Ventricular Tachycardia is especially of a concern, but according to my cardiologist, it's not uncommon for many people to have infrequent and brief episodes of Ventricular Tachycardia known as Non-Sustaining Ventricular Tachycardia (NSVT).

Tachycardia
https://www.mayoclinic.org/diseases-conditions/tachycardia/symptoms-causes/syc-20355127