There are only two people in the play, except the orator that make an entrance later. The other characters are invisible. Perhaps the Old Man och Old Women are the only ones left in the world. Perhaps an apocalypse has destroyed the earth, leaving nothing behind. They say that there is no Paris anymore, and talk about an old memory repeatedly. The chairs might symbolise their long lost friends. Another explanation is that the imaginary guests are real people, but with an absent mind. They are there, but at the same time not. However, despite being invisible, they seem more alive than the strange orator, who seems more like a robot than a human being. Are they in the future?
There are many themes in the play. The need to be remembered is easy to identify with. No one wants to be forgotten forever. When finding the meaning of life, or whatever discovery the Old Man has made, will garantee it. Perhaps the chairs symbolise the importance to not forget people. Or perhaps the couple might have dementia? Or being prisoners, bored and wanting to entertain themselves? It doesn't really matter. The play is about memories, and the ability to remember a past that was better than the present. It is about regret. The Old Woman often tells her husband what he could have become if he only were more ambitious. Now, when he has the answer to everything, and will reveal the secret to the world, he will finally be someone. He will be remembered.
The reason that the orator doesn't succeed to reveal the Old Man's discovery is perhaps because of the Old Man. He doesn't dare to reveal his discovery himself. Instead he escapes. If not believing in oneself, no one else does. He seems to have escaped many things in his life. He denies having a son and he admits having abandoned his dying mother. Is the empty room a form of escapism? The lack of responsibility is a great theme. By the way, perhaps the orator really tells the audience the meaning of life. They are just unable to understand it, because it's impossible to understand.
What's good about this play is that it makes you think. There are many interpretations possible, and the story surely means different things to different people.