The Orator is a pretty mysterious figure. Stage directions tell us that he's dressed as a typical nineteenth-century artist type and that he's kind of conceited. Other than that, we know nothing. We're not even sure if he's real. He may very well be just a part of the elderly couple's fantasy. The Old Man and Old Woman both seem a little surprised that he actually shows up in the flesh. In his stage directions, Ionesco says that "the Old Woman touches his [the Orator's] arm in order to assure herself that he exists" (488). The Old Man seems just as surprised at first. He cries out, "He exists. It's really he. This is not a dream!" (491). All this seems to support the idea that both the Old Man and Old Woman thought they were just playing make-believe all along.
There are a couple of arguments for the idea that Orator is a real person independent of the old couple's imaginations. For one, after the Old Man and Old Woman both kill themselves, the Orator stays on stage. If he only existed in their minds, wouldn't he just evaporate or something? Also, there's the very obvious fact that he is played by a real person.
Of course, even though the Orator is played by a real actor, Ionesco saw fit to include the stage direction, "the Orator must appear unreal" (488). Also, the Orator never reacts directly to the Old Man or Old Woman and instead only interacts with the invisible people. Very often it seems that, though, he is played by a real actor like the elderly couple, he is part of different world.
Ultimately, it's pretty much impossible to tell whether the Orator is real or not. We're pretty sure this ambiguity wasn't just laziness or confusion on Ionesco's part. One of the major tenants of both Existentialism and Absurdism is that there's no such thing as objective truth. Everything is totally subjective: whatever an individual thinks is real is what is real. If you think a giant pink bunny is coming to eat you, then it is. So, if the Old Man and Old Woman believe the Orator is there, he is there. It doesn't really matter if we believe in him or not. By forcing us to continually question the Orator's existence, Ionesco invites us to question whether anything around us is truly real. He forces us to confront the idea that perhaps everything is relative.