Taliesin Ben Beirdd actually existed. Though perhaps not everything told of his past could have been witnessed in the waking world.
I know exactly what you're wondering. It's what everyone thinks, when they first encounter the heroes of Welsh legend.
You pronounce his name: Taliesin (Tally-ess-sin) Ben Beirdd (Ben Beerth). The surname is a title translating as Chief Bard. But in this story, he hasn't earned that yet. His first name means Shining Brow. Nor has he acquired that epithet either, at the point where we come in.
Pull up to the fire and let me tell the tale of Taliesin.